Catalytic efficiency of flue gas filtration

ABSTRACT

Some embodiments of the present disclosure relate to a method of regenerating at least one filter medium comprising: providing at least one filter medium, wherein the at least one filter medium comprises: at least one catalyst material; and ammonium bisulfate (ABS) deposits, ammonium sulfate (AS) deposits, or any combination thereof; flowing a flue gas stream transverse to a cross-section of a filter medium, such that the flue gas stream passes through the cross section of the at least one filter medium, wherein the flue gas stream comprises: NOx compounds comprising: Nitric Oxide (NO), and Nitrogen Dioxide (NO 2 ); and increasing an NOx removal efficiency of the at least one filter medium after removal of deposits.

FIELD

The present disclosure relates to a filter medium, methods ofregenerating at least one filter medium, and methods of cleaning a fluegas stream.

BACKGROUND

Coal-fired power generation plants, municipal waste incinerators, andoil refinery plants generate large amounts of flue gases that containsubstantial varieties and quantities of environmental pollutants,nitrogen oxides (NO_(x) compounds), mercury (Hg) vapor, and particulatematters (PM). In the United States, burning coal alone generates about27 million tons of SO₂ and 45 tons of Hg each year. Thus, there is aneed for improvements to methods for removing NO_(x) compounds, sulfuroxides, mercury vapor, and fine particulate matters from industrial fluegases, such as coal-fired power plant flue gas.

SUMMARY

Some aspects of the present disclosure relate to a method comprising:

-   -   providing at least one filter medium;        -   wherein the at least one filter medium comprises:            -   at least one catalyst material; and            -   ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)                deposits, or any combination thereof;    -   flowing a flue gas stream transverse to a cross-section of the        at least one filter medium, such that the flue gas stream passes        through the cross section of the at least one filter medium,    -   wherein the flue gas stream comprises:        -   NO_(x) compounds comprising:            -   Nitric Oxide (NO), and            -   Nitrogen Dioxide (NO₂); and    -   increasing NO_(x) removal efficiency of the at least one filter        medium;        -   wherein the increasing of the NO_(x) removal efficiency of            the at least one filter medium comprises increasing an            upstream NO₂ concentration to a range from 2% to 99% of a            total concentration of the upstream NO_(x) compounds,            wherein increasing the upstream NO₂ concentration to a range            from 2% to 99% of a total concentration of the upstream            NO_(x) compounds comprises introducing additional NO₂ into            the flue gas stream; and            wherein the method regenerates the at least one filter            medium.

Some aspects of the present disclosure relate to a method comprising:

-   -   providing at least one filter medium        -   wherein the at least one filter medium comprises at least            one catalyst material;    -   flowing a flue gas stream transverse to a cross-section of the        at least one filter medium, such that the flue gas stream passes        through the cross section of the at least one filter medium from        an upstream side of the filter medium to a downstream side of        the filter medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂);            -   Sulfur Dioxide (SO₂); and            -   Ammonia (NH₃);    -   maintaining a constant NO_(x) removal efficiency of the at least        one filter medium;        -   wherein the maintaining a constant NO_(x) removal efficiency            of the at least one filter medium comprises:            -   providing an NO₂ concentration, measured from the                upstream side of the filter medium, in a range from 2%                to 99% of a total concentration of the NO_(x) compounds,                wherein providing the NO₂ concentration, measured from                the upstream side of the filter medium, in a range from                2% to 99% of a total concentration of the NO_(x)                compounds comprises introducing additional NO₂ into the                flue gas stream; and            -   controlling the NO₂ concentration, measured from the                downstream side of the filter medium, to a range of from                0.0001% to 0.5% of the concentration of the flue gas                stream;                wherein the method cleans the flue gas stream.

Some aspects of the present disclosure relate to a system comprising:

-   -   at least one filter medium,        -   wherein the at least one filter medium comprises:            -   an upstream side;            -   a downstream side;            -   at least one catalyst material; and            -   ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)                deposits, or        -   any combination thereof;    -   at least one filter bag,        -   wherein the at least one filter medium is disposed within            the at least one filter bag; and    -   at least one filter bag housing,        -   wherein the at least one filter bag is disposed within the            at least one filter bag housing;        -   wherein the at least one filter bag housing is configured to            receive a flow of a flue gas stream transverse to a            cross-section of the at least one filter medium, such that            the flue gas stream passes through the cross section of the            at least one filter medium from the upstream side of the at            least one filter medium to the downstream side of the at            least one filter medium,            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂); and    -   wherein the system is configured to increase a NO_(x) removal        efficiency of the at least one filter medium when an upstream        NO₂ concentration is increased to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds, and        wherein the upstream NO₂ concentration is increased to a range        from 2% to 99% of a total concentration of the upstream NO_(x)        compounds by introducing additional NO₂ into the flue gas        stream.

Some aspects of the present disclosure relate to a method comprising:

-   -   providing at least one filter medium        -   wherein the at least one filter medium comprises at least            one catalyst material;    -   flowing a flue gas stream transverse to a cross-section of the        at least one filter medium, such that the flue gas stream passes        through the cross section of the at least one filter medium from        an upstream side of the filter medium to a downstream side of        the filter medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂);            -   Sulfur Dioxide (SO₂); and            -   Ammonia (NH₃);    -   maintaining a NO_(x) removal efficiency of the at least one        filter medium in an amount of at least 70% of an initial NO_(x)        efficiency by:        -   providing an NO₂ concentration, measured from the upstream            side of the filter medium, in a range from 2% to 99% of a            total concentration of the NO_(x) compounds, wherein            providing the NO₂ concentration, measured from the upstream            side of the filter medium, in a range from 2% to 99% of a            total concentration of the NO_(x) compounds comprises            introducing additional NO₂ into the flue gas stream; and        -   controlling NO₂ concentration, measured from the downstream            side of the filter medium, to a range of from 0.0001% to            0.5% of the concentration of the flue gas stream            wherein the method cleans the flue gas stream.

Some aspects of the present disclosure relate to a method comprising:

-   -   providing at least one filter medium;        -   wherein the at least one filter medium comprises:            -   at least one catalyst material; and            -   ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)                deposits, or any combination thereof;    -   flowing a flue gas stream transverse to a cross-section of the        at least one filter medium, such that the flue gas stream passes        through the cross section of the at least one filter medium,        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂); and    -   increasing NO_(x) removal efficiency of the at least one filter        medium;        -   wherein the increasing of the NO_(x) removal efficiency of            the at least one filter medium comprises increasing an            upstream NO₂ concentration to a range from 2% to 99% of a            total concentration of the upstream NO_(x) compounds,            wherein increasing the upstream NO₂ concentration to a range            from 2% to 99% of a total concentration of the upstream            NO_(x) compounds comprises introducing at least one            oxidizing agent into the flue gas stream;            wherein the method regenerates the at least one filter            medium.

Some aspects of the present disclosure relate to a method comprising:

-   -   providing at least one filter medium        -   wherein the at least one filter medium comprises at least            one catalyst material;    -   flowing a flue gas stream transverse to a cross-section of the        at least one filter medium, such that the flue gas stream passes        through the cross section of the at least one filter medium from        an upstream side of the filter medium to a downstream side of        the filter medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂);            -   Sulfur Dioxide (SO₂); and            -   Ammonia (NH₃);    -   maintaining a constant NO_(x) removal efficiency of the at least        one filter medium;        -   wherein the maintaining a constant NO_(x) removal efficiency            of the at least one filter medium comprises:            -   providing an NO₂ concentration, measured from the                upstream side of the filter medium, in a range from 2%                to 99% of a total concentration of the NO_(x) compounds,                wherein providing the NO₂ concentration, measured from                the upstream side of the filter medium, in a range from                2% to 99% of a total concentration of the NO_(x)                compounds comprises introducing at least one oxidizing                agent into the flue gas stream; and            -   controlling the NO₂ concentration, measured from the                downstream side of the filter medium, to a range of from                0.0001% to 0.5% of the concentration of the flue gas                stream;                wherein the method cleans the flue gas stream.

Some aspects of the present disclosure relate to a system comprising:

-   -   at least one filter medium,        -   wherein the at least one filter medium comprises:            -   an upstream side;            -   a downstream side;            -   at least one catalyst material; and            -   ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)                deposits, or any combination thereof;    -   at least one filter bag,        -   wherein the at least one filter medium is disposed within            the at least one filter bag; and    -   at least one filter bag housing,        -   wherein the at least one filter bag is disposed within the            at least one filter bag housing;        -   wherein the at least one filter bag housing is configured to            receive a flow of a flue gas stream transverse to a            cross-section of the at least one filter medium, such that            the flue gas stream passes through the cross section of the            at least one filter medium from the upstream side of the at            least one filter medium to the downstream side of the at            least one filter medium,            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂); and    -   wherein the system is configured to increase an NO_(x) removal        efficiency of the at least one filter medium when an upstream        NO₂ concentration is increased to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds, and        wherein the upstream NO₂ concentration is increased to a range        from 2% to 99% of a total concentration of the upstream NO_(x)        compounds by introducing at least one oxidizing agent into the        flue gas stream.

Some aspects of the present disclosure relate to a method comprising:

-   -   providing at least one filter medium        -   wherein the at least one filter medium comprises at least            one catalyst material;    -   flowing a flue gas stream transverse to a cross-section of the        at least one filter medium, such that the flue gas stream passes        through the cross section of the at least one filter medium from        an upstream side of the filter medium to a downstream side of        the filter medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂);            -   Sulfur Dioxide (SO₂); and            -   Ammonia (NH₃);    -   maintaining a NO_(x) removal efficiency of the at least one        filter medium in an amount of at least 70% of an initial NO_(x)        efficiency by:        -   providing an NO₂ concentration, measured from the upstream            side of the filter medium, in a range from 2% to 99% of a            total concentration of the NO_(x) compounds, wherein            providing the NO₂ concentration, measured from the upstream            side of the filter medium, in a range from 2% to 99% of a            total concentration of the NO_(x) compounds comprises            introducing at least one oxidizing agent into the flue gas            stream; and        -   controlling NO₂ concentration, measured from the downstream            side of the filter medium, to a range of from 0.0001% to            0.5% of the concentration of the flue gas stream;            wherein the method cleans the flue gas stream.

DRAWINGS

Some embodiments of the disclosure are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theembodiments shown are by way of example and for purposes of illustrativediscussion of embodiments of the disclosure. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the disclosure may be practiced.

FIGS. 1A-1D depict embodiments of an exemplary filter medium andaccording to the present disclosure.

FIG. 2 depicts an exemplary NO_(x) removal efficiency after in-situflow-through regeneration by NO and NO₂ gas mixture on an exemplaryfilter medium.

FIG. 3 depicts an exemplary relative NO_(x) removal efficiency afterin-situ flow-through regeneration by NO and NO₂ gas mixture on anexemplary filter medium.

FIG. 4 depicts exemplary NO_(x) concentrations, measured from adownstream side of an exemplary filter medium, during the in-situ flowthrough regeneration by an NO and NO₂ mixture.

FIG. 5 depicts an exemplary relative NO_(x) removal efficiency afterin-situ flow-through regeneration by NO, NO₂ and NH₃ gas mixture on anexemplary filter medium.

FIG. 6 depicts an exemplary NO_(x) concentration, measured from adownstream side of an exemplar filter medium, during the in-situ flowthrough regeneration by a mixture comprising NO, NO₂, and NH₃.

FIG. 7 depicts an exemplary NO_(x) removal efficiency after in-situflow-by regeneration on an exemplary filter medium by a mixturecomprising NO, NO₂, and NH₃.

FIG. 8 depicts an exemplary NO_(x) removal efficiency after in-situflow-through regeneration on exemplary filter bags by a mixturecomprising NO, NO₂, and NH₃.

FIG. 9 depicts an example of “long term” NO_(x) removal efficiency withSO₂ and excess NO₂ in the downstream.

FIG. 10 depicts an example of “long term” NO_(x) removal efficiency withSO₂ but without excess NO₂ in the downstream.

FIG. 11 depicts an example of downstream NO₂ concentration in anexemplary “long term” NO_(x) removal efficiency measurement.

FIG. 12 depicts an example of NO_(x) removal efficiency and downstreamNO₂ concentration before, during and after in-situ flow-throughregeneration by NO, NO₂, and NH₃ mixture with exposure to SO₂.

FIG. 13 depicts an example of NO_(x) removal efficiency before, duringand after in-situ flow-through regeneration (148 hours) by NO, NO₂, andNH₃ mixture with exposure to SO₂.

FIG. 14 depicts NO_(x) removal efficiency with intermittent in-situflow-through regeneration by an exemplary NO, NO₂, and NH₃ mixture withexposure to SO₂.

FIG. 15 depicts an exemplary NO and NO₂ concentration change with uponinjection of 1 wt % hydrogen peroxide (H₂O₂) into a simulated flue gasstream comprising SO₂ and NO.

FIG. 16 depicts an exemplary NO to NO₂ percentage conversion uponinjection of 1 wt % H₂O₂ injection into a simulated flue gas streamcomprising SO₂ and NO at different temperatures.

FIG. 17 depicts an exemplary NO to NO₂ percentage conversion uponinjection of 0.3 wt % H₂O₂ injection into a simulated flue gas streamcomprising SO₂ and NO at different temperatures.

DETAILED DESCRIPTION

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this disclosure will become apparent from thefollowing description taken in conjunction with the accompanyingfigures. Detailed embodiments of the present disclosure are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the disclosure that may be embodied invarious forms. In addition, each of the examples given regarding thevarious embodiments of the disclosure which are intended to beillustrative, and not restrictive.

Throughout the specification and claims, the following terms take themeanings explicitly associated herein, unless the context clearlydictates otherwise. The phrases “in one embodiment,” “in an embodiment,”and “in some embodiments” as used herein do not necessarily refer to thesame embodiment(s), though it may. Furthermore, the phrases “in anotherembodiment” and “in some other embodiments” as used herein do notnecessarily refer to a different embodiment, although it may. Allembodiments of the disclosure are intended to be combinable withoutdeparting from the scope or spirit of the disclosure.

As used herein, the term “based on” is not exclusive and allows forbeing based on additional factors not described, unless the contextclearly dictates otherwise. In addition, throughout the specification,the meaning of “a,” “an,” and “the” include plural references. Themeaning of “in” includes “in” and “on.”

All prior patents, publications, and test methods referenced herein areincorporated by reference in their entireties.

As used herein, the term “flue gas stream” refers to a gaseous mixturethat comprises at least one byproduct of a combustion process (such as,but not limited to, a coal combustion process). In some embodiments, aflue gas stream may include at least one gas in an elevatedconcentration relative to a concentration resulting from the combustionprocess. For instance, in one non-limiting example, a flue gas streammay be subjected to a “scrubbing” process during which water vapor maybe added to the flue gas. Accordingly, in some such embodiments, theflue gas stream may include water vapor in an elevated concentrationrelative to the initial water vapor concentration due to combustion.Similarly, in some embodiments, a flue gas stream may include at leastone gas in a lesser concentration relative to an initial concentrationof the at least one gas output from the combustion process. This mayoccur, for example, by removing at least a portion at least one gasafter combustion. In some embodiments, a flue gas may take the form of agaseous mixture that is a combination of byproducts of multiplecombustion processes.

As used herein, the term “flow through” means that a flue gas stream isflowed transverse to a cross section of the at least one filter medium,such that the flue gas stream passes through a cross section of the atleast one filter medium. In some embodiments of a “flow through”configuration, the flue gas stream is flowed perpendicular to across-section of the at least one filter medium.

As used herein, the term “flow by” means that the flue gas stream is notflowed transverse to a cross section of the at least one filter medium,such that the flue gas does not pass through the cross section of the atleast one filter medium. In some embodiments of a “flow by”configuration, the flue gas stream is flowed parallel to a cross-sectionof the at least one filter medium.

As used herein “upstream” refers to a location of a flue gas streambefore entering a filter medium. In the “flow through” context,“upstream” may refer to the location of a flue gas stream beforeentering a cross section of a filter medium. In the “flow by” context,“upstream” may refer to the location of a flue gas stream beforeentering an enclosure (e.g., a housing, a filter bag, or other suitableenclosure described herein) that contains a filter medium.

As used herein “downstream” refers to a location of a flue gas streamafter exiting a filter medium. In the “flow through” context,“downstream” may refer to the location of a flue gas stream afterexiting a cross section of a filter medium. In the “flow by” context,“downstream” may refer to the location of a flue gas stream afterexiting an enclosure (e.g., a housing, a filter bag, or other suitableenclosure described herein) that contains a filter medium.

As used herein, the term “NO_(x) compound” refers to any oxide ofnitrogen. In some non-limiting embodiments, “NO_(x) compound” mayspecifically refer to gaseous oxides of nitrogen that are knownenvironmental pollutants.

As used herein, the term “catalytic composite article” set forth in theExamples refers to any material that includes a combination of at leastone catalyst material and at least one additional material according toany embodiment described herein. The additional material is not limitedto any particular type of material and may be, for example, a membrane,a felt batt, a ceramic substrate (including but not limited to a ceramiccandle), a honeycomb substrate, a monolith substrate, or any combinationthereof. The catalytic composite article may, in some non-limitingexamples, be a porous catalytic film.

Some embodiments of the present disclosure relate to a method ofregenerating at least one filter medium. As used herein, “regeneratingat least one filter medium” means that, after regeneration, the at leastone filter medium has a higher removal efficiency of at least onecomponent of the flue gas stream as compared to a removal efficiency ofthe at least one component of the flue gas stream, prior toregeneration. For example, in some non-limiting embodiments, afterregeneration, the at least one filter medium may have a higher removalefficiency of NO, NO₂, or combination thereof, as compared to a removalefficiency of the at least one component of the NO, NO₂, or combinationthereof, prior to regeneration.

In some embodiments, the at least one filter medium comprises at leastone catalyst material. In some embodiments, the at least one catalystmaterial comprises at least one of: Vanadium Monoxide (VO), VanadiumTrioxide (V₂O₃), Vanadium Dioxide (VO₂), Vanadium Pentoxide (V₂O₅),Tungsten Trioxide (WO₃), Molybdenum Trioxide (MoO₃), Titanium Dioxide(TiO₂), Silicon Dioxide (SiO₂), Aluminum Trioxide (Al₂O₃), ManganeseOxide (MnO₂), zeolites, or any combination thereof. In some embodiments,the at least one catalyst material is in the form of catalyst particles.

In some embodiments, the at least one filter medium comprises anupstream side and a downstream side. In some embodiments, the at leastone filter medium is disposed within at least one filter bag. In someembodiments, a plurality of filter mediums is disposed within a singlefilter bag. In some embodiments, the at least one filter bag is housedwithin at least one filter bag housing. In some embodiments, a pluralityof filter bags is disposed within a single filter bag housing.

In some embodiments, the one filter medium comprises a porous protectivelayer and a porous catalytic layer. In some embodiments, the porouscatalytic layer comprises at least one catalyst material. In someembodiments, the at least one catalyst material is disposed on theporous catalytic layer. In some embodiments, the at least one catalystmaterial is within (e.g., embedded within) the porous catalytic layer.

In some embodiments, the porous protective layer comprises a microporouslayer. In some embodiments, the microporous layer comprises an expandedpolytetrafluoroethylene (ePTFE) membrane.

In some embodiments, the at least one catalyst material is adhered tothe filter medium by at least one adhesive. In some embodiments, the atleast one catalyst material is adhered to the porous catalytic layer byat least one adhesive. In some exemplary embodiments, the at least onefilter medium is in the form of a filter bag, such that the adherence ofthe at least one catalyst material to the porous catalytic layer by theat least one adhesive form a coated filter bag. In some embodiments, theat least one catalyst material is in the form of catalyst particles,such that the coated filter bag is coated with the catalyst particles.

In some embodiments, the at least one adhesive is chosen frompolytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP),high molecular weight polyethylene (HMWPE), high molecular weightpolypropylene (HMWPP), perfluoroalkoxy alkane (PFA), polyvinylidenefluoride (PVDF), vinylidene fluoride (THV), chlorofluoroethylene (CFE),or any combination thereof. In some embodiments, the at least oneadhesive is selected from the group consisting ofpolytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP),high molecular weight polyethylene (HMWPE), high molecular weightpolypropylene (HMWPP), perfluoroalkoxy alkane (PFA), polyvinylidenefluoride (PVDF), vinylidene fluoride (THV), chlorofluoroethylene (CFE),and any combination thereof.

In some embodiments, the porous catalytic layer comprises at least onepolymeric substrate. In some embodiments, the at least one polymericsubstrate comprises a least one of: polytetrafluorethylene,poly(ethylene-co-tetrafluoroethylene), ultra-high molecular weightpolyethylene, polyparaxylylene, polylactic acid, polyimide, polyamide,polyaramid, polyphenylene sulfide, fiberglass, or any combinationthereof. In some embodiments, the at least one polymeric substrate isselected from the group consisting of: polytetrafluorethylene,poly(ethylene-co-tetrafluoroethylene), ultra-high molecular weightpolyethylene, polyparaxylylene, polylactic acid, polyimide, polyamide,polyaramid, polyphenylene sulfide, fiberglass, and any combinationthereof.

In some embodiments, the porous catalytic layer includes at least oneceramic substrate. In some embodiments, the at least one ceramicsubstrate is in the form of a ceramic candle described herein. In someembodiments, the one ceramic substrate comprises ceramic fibers. In someembodiments, the ceramic fibers comprise alkali metal silicates,alkaline earth metal silicates, aluminosilicates, or any combinationthereof.

In some embodiments, the porous catalytic layer is in the form of alayered assembly comprising a porous catalytic film and one or more feltbatts. In some embodiments, the one or more felt batts are positioned onat least one side of the porous catalytic film. In some embodiments, theporous catalytic film comprises the at least one catalyst material. Insome embodiments, the at least one catalyst material is disposed on theporous catalytic film. In some embodiments, the at least one catalystmaterial is within (e.g., embedded within) the porous catalytic film.

In some embodiments, the one or more felt batts comprise at least oneof: a polytetrafluoroethylene (PTFE) felt, a PTFE fleece, an expandedpolytetrafluoroethylene (ePTFE) felt, an ePTFE fleece, a wovenfluoropolymer staple fiber, a nonwoven fluoropolymer staple fiber, orany combination thereof. In some embodiments, the one or more felt battsare selected from the group consisting of: a polytetrafluoroethylene(PTFE) felt, a PTFE fleece, an expanded polytetrafluoroethylene (ePTFE)felt, an ePTFE fleece, a woven fluoropolymer staple fiber, a nonwovenfluoropolymer staple fiber, and any combination thereof.

In some embodiments, the porous catalytic film comprises a membrane. Insome embodiments, the porous catalytic film comprises a polymermembrane. In some embodiments, the porous catalytic film comprises afluoropolymer membrane and may be referred to as a porous catalyticfluoropolymer film. In some embodiments, the porous catalytic filmcomprises an expanded polytetrafluoroethylene (ePTFE) membrane.

In some embodiments, the porous catalytic film comprises catalystparticles enmeshed within the ePTFE membrane. In some embodiments, theePTFE membrane has a microstructure that includes nodes, fibrils, or anycombination thereof. In some embodiments, the catalyst particles may beenmeshed into the microstructure. In some embodiments, the catalystparticles may be enmeshed into the nodes. In some embodiments, thecatalyst particles may be enmeshed into the fibrils. In someembodiments, the catalyst particles may be enmeshed into the nodes andfibrils.

In some embodiments, the at least one filter medium is in the form of aceramic candle. In some embodiments, the ceramic candle comprises atleast one ceramic material. In some embodiments, the least one ceramicmaterial is chosen from: silica-aluminate, calcium-magnesium-silicate,calcium-silicate fibers, or any combination thereof. In someembodiments, catalyst particles form a coating on the at least oneceramic material.

In some embodiments, the at least one filter medium may comprise anymaterial configured to capture at least one of solid particulates,liquid aerosols, or any combination thereof from a flue gas stream. Insome embodiments, the at least one filter medium is in the form of atleast one of: a filter bag, a honeycomb, a monolith or any combinationthereof.

In some embodiments, the at least filter medium comprises ammoniumbisulfate (ABS) deposits, ammonium sulfate (AS) deposits, or anycombination thereof. In some embodiments, ABS deposits are disposed onthe at least one catalyst material of the at least one filter medium. Insome embodiments, ABS deposits are disposed within the at least onecatalyst material of the at least one filter medium. In someembodiments, at least some of the ABS deposits, AS deposits, or anycombination thereof may be removed, so as to increase a removalefficiency (e.g., NO_(x) removal efficiency) of the at least one filtermedium, as described in further detail herein, infra.

In some embodiments, the ABS deposits are present in a concentrationranging from 0.01% to 99% by mass of the at least one filter mediumduring the providing step. In some embodiments, the ABS deposits arepresent in a concentration ranging from 0.1% to 99% by mass of the atleast one filter medium during the providing step. In some embodiments,the ABS deposits are present in a concentration ranging from 1% to 99%by mass of the at least one filter medium during the providing step. Insome embodiments, the ABS deposits are present in a concentrationranging from 10% to 99% by mass of the at least one filter medium duringthe providing step. In some embodiments, the ABS deposits are present ina concentration ranging from 25% to 99% by mass of the at least onefilter medium during the providing step. In some embodiments, the ABSdeposits are present in a concentration ranging from 50% to 99% by massof the at least one filter medium during the providing step. In someembodiments, the ABS deposits are present in a concentration rangingfrom 75% to 99% by mass of the at least one filter medium during theproviding step. In some embodiments, the ABS deposits are present in aconcentration ranging from 95% to 99% by mass of the at least one filtermedium during the providing step.

In some embodiments, the ABS deposits are present in a concentrationranging from 0.01% to 95% by mass of the at least one filter mediumduring the providing step. In some embodiments, the ABS deposits arepresent in a concentration ranging from 0.01% to 75% by mass of the atleast one filter medium during the providing step. In some embodiments,the ABS deposits are present in a concentration ranging from 0.01% to50% by mass of the at least one filter medium during the providing step.In some embodiments, the ABS deposits are present in a concentrationranging from 0.01% to 25% by mass of the at least one filter mediumduring the providing step. In some embodiments, the ABS deposits arepresent in a concentration ranging from 0.01% to 10% by mass of the atleast one filter medium during the providing step. In some embodiments,the ABS deposits are present in a concentration ranging from 0.01% to 1%by mass of the at least one filter medium during the providing step. Insome embodiments, the ABS deposits are present in a concentrationranging from 0.01% to 0.1% by mass of the at least one filter mediumduring the providing step.

In some embodiments, the ABS deposits are present in a concentrationranging from 0.1% to 95% by mass of the at least one filter mediumduring the providing step. In some embodiments, the ABS deposits arepresent in a concentration ranging from 1% to 75% by mass of the atleast one filter medium during the providing step. In some embodiments,the ABS deposits are present in a concentration ranging from 10% to 50%by mass of the at least one filter medium during the providing step.

In some embodiments, the method of regenerating at least one filtermedium comprises flowing a flue gas stream through the at least onefilter medium (i.e., transverse to a cross-section of the at least onefilter medium), such that the flue gas stream passes through the crosssection of the at least one filter medium. In some embodiments, the fluegas stream is flowed from an upstream side to a downstream side of theat least one filter medium. In some embodiments, the flue gas stream isflowed perpendicular to a cross-section of the at least one filtermedium.

In some embodiments, the method of regenerating at least one filtermedium comprises flowing a flue gas stream by the at least one filtermedium (i.e., non-transverse to a cross-section of the at least onefilter medium), such that the flue gas stream does not pass through thecross section of the at least one filter medium. In some embodiments,the flue gas stream is flowed parallel to a cross-section of the atleast one filter medium.

In some embodiments, the temperature of the flue gas stream ranges from160° C. to 280° C. during the flowing step. In some embodiments, thetemperature of the flue gas stream ranges from 175° C. to 280° C. duringthe flowing step. In some embodiments, the temperature of the flue gasstream ranges from 200° C. to 280° C. during the flowing step. In someembodiments, the temperature of the flue gas stream ranges from 225° C.to 280° C. during the flowing step. In some embodiments, the temperatureof the flue gas stream ranges from 250° C. to 280° C. during the flowingstep.

In some embodiments, the temperature of the flue gas stream ranges from160° C. to 250° C. during the flowing step. In some embodiments, thetemperature of the flue gas stream ranges from 160° C. to 225° C. duringthe flowing step. In some embodiments, the temperature of the flue gasstream ranges from 160° C. to 200° C. during the flowing step. In someembodiments, the temperature of the flue gas stream ranges from 160° C.to 175° C. during the flowing step.

In some embodiments, the temperature of the flue gas stream ranges from175° C. to 250° C. during the flowing step. In some embodiments, thetemperature of the flue gas stream ranges from 200° C. to 225° C. duringthe flowing step.

In some embodiments, such as embodiments where the at least one filtermedium is in the form of or comprises a ceramic substrate (e.g., aceramic candle), the temperature of the flue gas stream ranges from 170°C. to 450° C. during the flowing step. In some embodiments, such asembodiments where the at least one filter medium is in the form of orcomprises a ceramic substrate (e.g., a ceramic candle), the temperatureof the flue gas stream ranges from 200° C. to 450° C. during the flowingstep. In some embodiments, such as embodiments where the at least onefilter medium is in the form of or comprises a ceramic substrate (e.g.,a ceramic candle), the temperature of the flue gas stream ranges from250° C. to 450° C. during the flowing step. In some embodiments, such asembodiments where the at least one filter medium is in the form of orcomprises a ceramic substrate (e.g., a ceramic candle), the temperatureof the flue gas stream ranges from 300° C. to 450° C. during the flowingstep. In some embodiments, such as embodiments where the at least onefilter medium is in the form of or comprises a ceramic substrate (e.g.,a ceramic candle), the temperature of the flue gas stream ranges from350° C. to 450° C. during the flowing step. In some embodiments, such asembodiments where the at least one filter medium is in the form of orcomprises a ceramic substrate (e.g., a ceramic candle), the temperatureof the flue gas stream ranges from 400° C. to 450° C. during the flowingstep.

In some embodiments, such as embodiments where the at least one filtermedium is in the form of or comprises a ceramic substrate (e.g., aceramic candle), the temperature of the flue gas stream ranges from 170°C. to 400° C. during the flowing step. In some embodiments, such asembodiments where the at least one filter medium is in the form of orcomprises a ceramic substrate (e.g., a ceramic candle), the temperatureof the flue gas stream ranges from 170° C. to 350° C. during the flowingstep. In some embodiments, such as embodiments where the at least onefilter medium is in the form of or comprises a ceramic substrate (e.g.,a ceramic candle), the temperature of the flue gas stream ranges from170° C. to 300° C. during the flowing step. In some embodiments, such asembodiments where the at least one filter medium is in the form of orcomprises a ceramic substrate (e.g., a ceramic candle), the temperatureof the flue gas stream ranges from 170° C. to 250° C. during the flowingstep. In some embodiments, such as embodiments where the at least onefilter medium is in the form of or comprises a ceramic substrate (e.g.,a ceramic candle), the temperature of the flue gas stream ranges from170° C. to 200° C. during the flowing step.

In some embodiments, such as embodiments where the at least one filtermedium is in the form of a or comprises ceramic substrate (e.g., aceramic candle), the temperature of the flue gas stream ranges from 200°C. to 400° C. during the flowing step. In some embodiments, such asembodiments where the at least one filter medium is in the form of orcomprises a ceramic substrate (e.g., a ceramic candle), the temperatureof the flue gas stream ranges from 250° C. to 350° C. during the flowingstep.

In some embodiments, the flue gas stream comprises NO_(x) compounds. Insome embodiments, the NO_(x) compounds comprise Nitric Oxide (NO) andNitrogen Dioxide (NO₂). In some embodiments, the flue gas stream furthercomprises at least one of Oxygen (O₂), Water (H₂O), Nitrogen (N₂),Carbon Monoxide (CO), Sulfur Dioxide (SO₂), Sulfur Trioxide (SO₃), oneor more hydrocarbons, or any combination thereof.

In some embodiments, the method of regenerating at least one filtermedium comprises increasing NO_(x) removal efficiency of the at leastone filter medium. In some embodiments, this increase in NO_(x) removalefficiency may occur as a result of removing ABS deposits, AS deposits,or any combination thereof.

In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 2% to 99% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 5% to 99% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 10% to 99% of a total concentration of the NO_(x)compounds. In some embodiments, the increasing of the NO_(x) removalefficiency of the at least one filter medium comprises increasing NO₂concentration to a range from 25% to 99% of a total concentration of theNO_(x) compounds. In some embodiments, the increasing of the NO_(x)removal efficiency of the at least one filter medium comprisesincreasing NO₂ concentration to a range from 50% to 99% of a totalconcentration of the NO_(x) compounds. In some embodiments, theincreasing of the NO_(x) removal efficiency of the at least one filtermedium comprises increasing NO₂ concentration to a range from 75% to 99%of a total concentration of the NO_(x) compounds. In some embodiments,the increasing of the NO_(x) removal efficiency of the at least onefilter medium comprises increasing NO₂ concentration to a range from 95%to 99% of a total concentration of the NO_(x) compounds.

In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 2% to 95% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 2% to 75% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 2% to 50% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 2% to 25% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 2% to 10% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 2% to 5% of a total concentration of the NO_(x) compounds.

In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 5% to 95% of a total concentration of the NO_(x) compounds.In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium comprises increasing NO₂ concentration toa range from 10% to 75% of a total concentration of the NO_(x)compounds. In some embodiments, the increasing of the NO_(x) removalefficiency of the at least one filter medium comprises increasing NO₂concentration to a range from 25% to 50% of a total concentration of theNO_(x) compounds.

In some embodiments, the concentration of NO₂ is increased byintroducing at least one oxidizing agent to the flue gas stream.

In some embodiments, the concentration of NO₂ is increased byintroducing at least one oxidizing agent to the flue gas stream in anamount ranging from 0.001 wt % to 50 wt % based on a total weight of theflue gas stream. In some embodiments, the concentration of NO₂ isincreased by introducing at least one oxidizing agent to the flue gasstream in an amount ranging from 0.01 wt % to 50 wt % based on a totalweight of the flue gas stream. In some embodiments, the concentration ofNO₂ is increased by introducing at least one oxidizing agent to the fluegas stream in an amount ranging from 0.1 wt % to 50 wt % based on atotal weight of the flue gas stream. In some embodiments, theconcentration of NO₂ is increased by introducing at least one oxidizingagent to the flue gas stream in an amount ranging from 1 wt % to 50 wt %based on a total weight of the flue gas stream. In some embodiments, theconcentration of NO₂ is increased by introducing at least one oxidizingagent to the flue gas stream in an amount ranging from 10 wt % to 50 wt% based on a total weight of the flue gas stream. In some embodiments,the concentration of NO₂ is increased by introducing at least oneoxidizing agent to the flue gas stream in an amount ranging from 20 wt %to 50 wt % based on a total weight of the flue gas stream. In someembodiments, the concentration of NO₂ is increased by introducing atleast one oxidizing agent to the flue gas stream in an amount rangingfrom 30 wt % to 50 wt % based on a total weight of the flue gas stream.In some embodiments, the concentration of NO₂ is increased byintroducing at least one oxidizing agent to the flue gas stream in anamount ranging from 40 wt % to 50 wt % based on a total weight of theflue gas stream.

In some embodiments, the concentration of NO₂ is increased byintroducing at least one oxidizing agent to the flue gas stream in anamount ranging from 0.001 wt % to 40 wt % based on a total weight of theflue gas stream. In some embodiments, the concentration of NO₂ isincreased by introducing at least one oxidizing agent to the flue gasstream in an amount ranging from 0.001 wt % to 30 wt % based on a totalweight of the flue gas stream. In some embodiments, the concentration ofNO₂ is increased by introducing at least one oxidizing agent to the fluegas stream in an amount ranging from 0.001 wt % to 20 wt % based on atotal weight of the flue gas stream. In some embodiments, theconcentration of NO₂ is increased by introducing at least one oxidizingagent to the flue gas stream in an amount ranging from 0.001 wt % to 10wt % based on a total weight of the flue gas stream. In someembodiments, the concentration of NO₂ is increased by introducing atleast one oxidizing agent to the flue gas stream in an amount rangingfrom 0.001 wt % to 1 wt % based on a total weight of the flue gasstream. In some embodiments, the concentration of NO₂ is increased byintroducing at least one oxidizing agent to the flue gas stream in anamount ranging from 0.001 wt % to 0.1 wt % based on a total weight ofthe flue gas stream. In some embodiments, the concentration of NO₂ isincreased by introducing at least one oxidizing agent to the flue gasstream in an amount ranging from 0.001 wt % to 0.01 wt % based on atotal weight of the flue gas stream.

In some embodiments, the concentration of NO₂ is increased byintroducing at least one oxidizing agent to the flue gas stream in anamount ranging from 0.01 wt % to 40 wt % based on a total weight of theflue gas stream. In some embodiments, the concentration of NO₂ isincreased by introducing at least one oxidizing agent to the flue gasstream in an amount ranging from 0.1 wt % to 30 wt % based on a totalweight of the flue gas stream. In some embodiments, the concentration ofNO₂ is increased by introducing at least one oxidizing agent to the fluegas stream in an amount ranging from 1 wt % to 20 wt % based on a totalweight of the flue gas stream.

In some embodiments, the at least one oxidizing agent comprises anorganic peroxide, a metal peroxide, a peroxy-acid, or any combinationthereof.

Examples of at least one organic peroxide that may be suitable for someembodiments of the present disclosure include, but are not limited to,acetyl acetone peroxide, acetyl benzoyl peroxide, tert-butylhydroperoxide, di-(1-naphthoyl)peroxide, diacetyl peroxide, ethylhydroperoxide, methyl ethyl ketone peroxide, methyl isobutyl ketoneperoxide, or any combination thereof. Examples of at least one metalperoxide that may be suitable for some embodiments of the presentdisclosure include but are not limited to barium peroxide (BaO₂), sodiumperoxide (Na₂O₂), or any combination thereof.

Examples of at least one peroxy-acid that may be suitable for someembodiments of the present disclosure include, but are not limited to,peroxymonosulfuric acid (H₂SO₅), peroxynitric acid (HNO₄),peroxymonophosphoric acid (H₃PO₅), or any combination thereof.

Further examples of at least one oxidizing agent that may be suitablefor some embodiments of the present disclosure include, but are notlimited to, sodium percarbonate (Na₂H₃CO₆), sodium perborate(Na₂H₄B₂O₈), potassium persulfate (K₂S₂₀₈) potassium permanganate(KMnO₄) sodium hypochlorite (NaClO), calcium hypochlorite (Ca(ClO)),chlorine dioxide (ClO₂) potassium chlorate (KClO₃), sodium chlorate(NaClO₃), magnesium chlorate (Mg(ClO₃)₂) ammonium perchlorate (NH₄ClO₄),perchloric acid (HClO₄), potassium perchlorate (KClO₄), sodiumperchlorate (NaClO₄), sodium chlorite (NaClO₂), lithium hypochlorite(LiOCl), calcium hypochlorite Ca(OCl)₂, barium hypochlorite Ba(ClO)₂,sodium hypochlorite (NaClO), sodium bismuthate (NaBiO₃), or anycombination thereof.

In some embodiments, the at least one oxidizing agent is chosen from:hydrogen peroxide (H₂O₂), ozone (O₃), hydroxyl radical or anycombination thereof. In some embodiments, the at least one oxidizingagent is selected from the group consisting of: H₂O₂, O₃, hydroxylradical, and any combination thereof.

In some embodiments, the at least one oxidizing agent comprises,consists of, or consists essentially of H₂O₂.

In some embodiments, the H₂O₂ is introduced into the flue gas stream ina sufficient amount so as to oxidize at least some of the NO in the fluegas stream to NO₂. In some embodiments, the sufficient amount of H₂O₂that is introduced into the flue gas stream is an amount sufficient tooxidize at least 10% of the NO concentration in the flue gas stream toNO₂. In some embodiments, the sufficient amount of H₂O₂ that isintroduced into the flue gas stream is an amount sufficient to oxidizeat least 20% of the NO concentration in the flue gas stream to NO₂. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is an amount sufficient to oxidize at least 30% ofthe NO concentration in the flue gas stream to NO₂. In some embodiments,the sufficient amount of H₂O₂ that is introduced into the flue gasstream is an amount sufficient to oxidize at least 40% of the NOconcentration in the flue gas stream to NO₂. In some embodiments, thesufficient amount of H₂O₂ that is introduced into the flue gas stream isan amount sufficient to oxidize at least 50% of the NO concentration inthe flue gas stream to NO₂. In some embodiments, the sufficient amountof H₂O₂ that is introduced into the flue gas stream is an amountsufficient to oxidize at least 60% of the NO concentration in the fluegas stream to NO₂. In some embodiments, the sufficient amount of H₂O₂that is introduced into the flue gas stream is an amount sufficient tooxidize at least 70% of the NO concentration in the flue gas stream toNO₂. In some embodiments, the sufficient amount of H₂O₂ that isintroduced into the flue gas stream is an amount sufficient to oxidizeat least 80% of the NO concentration in the flue gas stream to NO₂. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is an amount sufficient to oxidize at least 90% ofthe NO concentration in the flue gas stream to NO₂. In some embodiments,the sufficient amount of H₂O₂ that is introduced into the flue gasstream is an amount sufficient to oxidize at least 95% of the NOconcentration in the flue gas stream to NO₂. In some embodiments, thesufficient amount of H₂O₂ that is introduced into the flue gas stream isan amount sufficient to oxidize at least all of the NO concentration inthe flue gas stream to NO₂.

In some embodiments, the sufficient amount of H₂O₂ that is introducedinto the flue gas stream is an amount sufficient to oxidize 10% to 90%of the NO concentration in the flue gas stream to NO₂. In someembodiments, the sufficient amount of H₂O₂ that is introduced into theflue gas stream is an amount sufficient to oxidize 20% to 90% of the NOconcentration in the flue gas stream to NO₂. In some embodiments, thesufficient amount of H₂O₂ that is introduced into the flue gas stream isan amount sufficient to oxidize 30% to 90% of the NO concentration inthe flue gas stream to NO₂. In some embodiments, the sufficient amountof H₂O₂ that is introduced into the flue gas stream is an amountsufficient to oxidize 40% to 90% of the NO concentration in the flue gasstream to NO₂. In some embodiments, the sufficient amount of H₂O₂ thatis introduced into the flue gas stream is an amount sufficient tooxidize 50% to 90% of the NO concentration in the flue gas stream toNO₂. In some embodiments, the sufficient amount of H₂O₂ that isintroduced into the flue gas stream is an amount sufficient to oxidize60% to 90% of the NO concentration in the flue gas stream to NO₂. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is an amount sufficient to oxidize 70% to 90% of theNO concentration in the flue gas stream to NO₂. In some embodiments, thesufficient amount of H₂O₂ that is introduced into the flue gas stream isan amount sufficient to oxidize 80% to 90% of the NO concentration inthe flue gas stream to NO₂.

In some embodiments, the sufficient amount of H₂O₂ that is introducedinto the flue gas stream is an amount sufficient to oxidize 10% to 80%of the NO concentration in the flue gas stream to NO₂. In someembodiments, the sufficient amount of H₂O₂ that is introduced into theflue gas stream is an amount sufficient to oxidize 20% to 70% of the NOconcentration in the flue gas stream to NO₂. In some embodiments, thesufficient amount of H₂O₂ that is introduced into the flue gas stream isan amount sufficient to oxidize 30% to 60% of the NO concentration inthe flue gas stream to NO₂. In some embodiments, the sufficient amountof H₂O₂ that is introduced into the flue gas stream is an amountsufficient to oxidize 30% to 50% of the NO concentration in the flue gasstream to NO₂. In some embodiments, the sufficient amount of H₂O₂ thatis introduced into the flue gas stream is an amount sufficient tooxidize 40% to 50% of the NO concentration in the flue gas stream toNO₂.

In some embodiments, the sufficient amount of H₂O₂ that is introducedinto the flue gas stream is 0.1 wt % H₂O₂ to 30 wt % H₂O₂ based on atotal weight of the flue gas stream. In some embodiments, the sufficientamount of H₂O₂ that is introduced into the flue gas stream is 1 wt %H₂O₂ to 30 wt % H₂O₂ based on a total weight of the flue gas stream. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is 5 wt % H₂O₂ to 30 wt % H₂O₂ based on a totalweight of the flue gas stream. In some embodiments, the sufficientamount of H₂O₂ that is introduced into the flue gas stream is 10 wt %H₂O₂ to 30 wt % H₂O₂ based on a total weight of the flue gas stream. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is 15 wt % H₂O₂ to 30 wt % H₂O₂ based on a totalweight of the flue gas stream. In some embodiments, the sufficientamount of H₂O₂ that is introduced into the flue gas stream is 20 wt %H₂O₂ to 30 wt % H₂O₂ based on a total weight of the flue gas stream. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is 25 wt % H₂O₂ to 30 wt % H₂O₂ based on a totalweight of the flue gas stream.

In some embodiments, the sufficient amount of H₂O₂ that is introducedinto the flue gas stream is 0.1 wt % H₂O₂ to 25 wt % H₂O₂ based on atotal weight of the flue gas stream. In some embodiments, the sufficientamount of H₂O₂ that is introduced into the flue gas stream is 0.1 wt %H₂O₂ to 20 wt % H₂O₂ based on a total weight of the flue gas stream. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is 0.1 wt % H₂O₂ to 15 wt % H₂O₂ based on a totalweight of the flue gas stream. In some embodiments, the sufficientamount of H₂O₂ that is introduced into the flue gas stream is 0.1 wt %H₂O₂ to 10 wt % H₂O₂ based on a total weight of the flue gas stream. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is 0.1 wt % H₂O₂ to 5 wt % H₂O₂ based on a totalweight of the flue gas stream. In some embodiments, the sufficientamount of H₂O₂ that is introduced into the flue gas stream is 0.1 wt %H₂O₂ to 1 wt % H₂O₂ based on a total weight of the flue gas stream.

In some embodiments, the sufficient amount of H₂O₂ that is introducedinto the flue gas stream is 1 wt % H₂O₂ to 25 wt % H₂O₂ based on a totalweight of the flue gas stream. In some embodiments, the sufficientamount of H₂O₂ that is introduced into the flue gas stream is 5 wt %H₂O₂ to 20 wt % H₂O₂ based on a total weight of the flue gas stream. Insome embodiments, the sufficient amount of H₂O₂ that is introduced intothe flue gas stream is 10 wt % H₂O₂ to 15 wt % H₂O₂ based on a totalweight of the flue gas stream.

In some embodiments, the oxidation of at least some of the NO in theflue gas stream to NO₂ results in the NO₂ having an upstreamconcentration in a range from 2% to 99% of a total concentration of theNO_(x) compounds. In some embodiments, the oxidation of at least some ofthe NO in the flue gas stream to NO₂ results in the NO₂ having anupstream concentration in a range from 10% to 99% of a totalconcentration of the NO_(x) compounds. In some embodiments, theoxidation of at least some of the NO in the flue gas stream to NO₂results in the NO₂ having an upstream concentration in a range from 25%to 99% of a total concentration of the NO_(x) compounds. In someembodiments, the oxidation of at least some of the NO in the flue gasstream to NO₂ results in the NO₂ having an upstream concentration in arange from 50% to 99% of a total concentration of the NO_(x) compounds.In some embodiments, the oxidation of at least some of the NO in theflue gas stream to NO₂ results in the NO₂ having an upstreamconcentration in a range from 75% to 99% of a total concentration of theNO_(x) compounds. In some embodiments, the oxidation of at least some ofthe NO in the flue gas stream to NO₂ results in the NO₂ having anupstream concentration in a range from 90% to 99% of a totalconcentration of the NO_(x) compounds.

In some embodiments, the oxidation of at least some of the NO in theflue gas stream to NO₂ results in the NO₂ having an upstreamconcentration in a range from 2% to 90% of a total concentration of theNO_(x) compounds. In some embodiments, the oxidation of at least some ofthe NO in the flue gas stream to NO₂ results in the NO₂ having anupstream concentration in a range from 2% to 75% of a totalconcentration of the NO_(x) compounds. In some embodiments, theoxidation of at least some of the NO in the flue gas stream to NO₂results in the NO₂ having an upstream concentration in a range from 2%to 50% of a total concentration of the NO_(x) compounds. In someembodiments, the oxidation of at least some of the NO in the flue gasstream to NO₂ results in the NO₂ having an upstream concentration in arange from 2% to 25% of a total concentration of the NO_(x) compounds.In some embodiments, the oxidation of at least some of the NO in theflue gas stream to NO₂ results in the NO₂ having an upstreamconcentration in a range from 2% to 10% of a total concentration of theNO_(x) compounds.

In some embodiments, the oxidation of at least some of the NO in theflue gas stream to NO₂ results in the NO₂ having an upstreamconcentration in a range from 10% to 90% of a total concentration of theNO_(x) compounds. In some embodiments, the oxidation of at least some ofthe NO in the flue gas stream to NO₂ results in the NO₂ having anupstream concentration in a range from 10% to 75% of a totalconcentration of the NO_(x) compounds. In some embodiments, theoxidation of at least some of the NO in the flue gas stream to NO₂results in the NO₂ having an upstream concentration in a range from 25%to 50% of a total concentration of the NO_(x) compounds.

In some embodiments, the concentration of NO₂ is increased byintroducing additional NO₂ into the flue gas stream. In someembodiments, at least some of the additional NO₂ is introduced byoxidizing at least some of the NO in the flue gas stream to NO₂ with theat least one oxidizing agent described herein. In some embodiments, theadditional NO₂ is introduced directly into the flue gas stream, e.g., byat least one gas injection system. In some embodiments, additional NO₂may be introduced by a combination of direct introduction andoxidization. In some embodiments, introducing additional NO₂ comprisesremoving at least some of the NO in the flue gas stream from the fluegas stream, oxidizing the NO to NO₂, and reintroducing at least some ofthe resulting NO₂ into the flue gas stream. In some embodiments, theresulting NO₂ may be reintroduced into the flue gas stream as a gasmixture comprising NO and NO₂.

In some embodiments, the increasing of the NO_(x) removal efficiency ofthe at least one filter medium further comprises adding ammonia (NH₃).In some embodiments, cleaning a flue gas stream (as described herein,infra) comprises adding NH₃. In some embodiments, a combination ofcleaning the flue gas stream and regenerating the at least one filtermedium comprises adding NH₃.

In some embodiments, NH₃ is added in a concentration ranging from0.0001% to 0.5% of the concentration of the flue gas stream. In someembodiments, NH₃ is added in a concentration ranging from 0.001% to 0.5%of the concentration of the flue gas stream. In some embodiments, NH₃ isadded in a concentration ranging from 0.01% to 0.5% of the concentrationof the flue gas stream. In some embodiments, NH₃ is added in aconcentration ranging from 0.1% to 0.5% of the concentration of the fluegas stream.

In some embodiments, NH₃ is added in a concentration ranging from0.0001% to 0.1% of the concentration of the flue gas stream. In someembodiments, NH₃ is added in a concentration ranging from 0.0001% to0.05% of the concentration of the flue gas stream. In some embodiments,NH₃ is added in a concentration ranging from 0.0001% to 0.005% of theconcentration of the flue gas stream.

In some embodiments, NH₃ is added in a concentration ranging from 0.005%to 0.1% of the concentration of the flue gas stream. In someembodiments, NH₃ is added in a concentration ranging from 0.005% to0.05% of the concentration of the flue gas stream.

In some embodiments, the NO_(x) removal efficiency of the at least onefilter medium is at least 0.5% higher after the increasing step thanduring the providing step. In some embodiments, the NO_(x) removalefficiency of the at least one filter medium is at least 1% higher afterthe increasing step than during the providing step. In some embodiments,the NO_(x) removal efficiency of the at least one filter medium is atleast 5% higher after the increasing step than during the providingstep. In some embodiments, the NO_(x) removal efficiency of the at leastone filter medium is at least 10% higher after the increasing step thanduring the providing step. In some embodiments, the NO_(x) removalefficiency of the at least one filter medium is at least 25% higherafter the increasing step than during the providing step. In someembodiments, the NO_(x) removal efficiency of the at least one filtermedium is at least 50% higher after the increasing step than during theproviding step. In some embodiments, the NO_(x) removal efficiency ofthe at least one filter medium is at least 75% higher after theincreasing step than during the providing step. In some embodiments, theNO_(x) removal efficiency of the at least one filter medium is at least100% higher after the increasing step than during the providing step.

In some embodiments, the increasing of the NO_(x) removal efficiencycomprises removing at least some of the ABS deposits, the AS deposits,or any combination thereof, from the at least one filter medium. In someembodiments, removing at least some of the ABS deposits, the ASdeposits, or any combination thereof, from the at least one filtermedium may regenerate the at least one filter medium, as describedherein.

In some embodiments, the increasing of the NO_(x) removal efficiencycomprises removing at least 10% of the ABS deposits, the AS deposits, orany combination thereof, from the at least one filter medium. In someembodiments, the increasing of the NO_(x) removal efficiency comprisesremoving at least 25% of the ABS deposits, the AS deposits, or anycombination thereof, from the at least one filter medium. In someembodiments, the increasing of the NO_(x) removal efficiency comprisesremoving at least 50% of the ABS deposits, the AS deposits, or anycombination thereof, from the at least one filter medium. In someembodiments, the increasing of the NO_(x) removal efficiency comprisesremoving at least 75% of the ABS deposits, the AS deposits, or anycombination thereof, from the at least one filter medium. In someembodiments, the increasing of the NO_(x) removal efficiency comprisesremoving at least 95% of the ABS deposits, the AS deposits, or anycombination thereof, from the at least one filter medium. In someembodiments, the increasing of the NO_(x) removal efficiency comprisesremoving all of the ABS deposits, the AS deposits, or any combinationthereof, from the at least one filter medium.

In some embodiments, after the step of increasing the NO_(x) removalefficiency, ABS deposits are disposed on the catalyst material of the atleast one filter medium in a concentration ranging from 0.01% to 98% bymass of the at least one filter medium. In some embodiments after thestep of increasing the NO_(x) removal efficiency, ABS deposits aredisposed on the catalyst material of the at least one filter medium in aconcentration ranging from 0.01% to 90% by mass of the at least onefilter medium. In some embodiments, after the step of increasing theNO_(x) removal efficiency, ABS deposits are disposed on the catalystmaterial of the at least one filter medium in a concentration rangingfrom 0.01% to 50% by mass of the at least one filter medium. In someembodiments, after the step of increasing the NO_(x) removal efficiency,ABS deposits are disposed on the catalyst material of the at least onefilter medium in a concentration ranging from 0.01% to 20% by mass ofthe at least one filter medium. In some embodiments, after the step ofincreasing the NO_(x) removal efficiency, ABS deposits are disposed onthe catalyst material of the at least one filter medium in aconcentration ranging from 0.01% to 10% by mass of the at least onefilter medium. In some embodiments, after the step of increasing theNO_(x) removal efficiency, ABS deposits are disposed on the catalystmaterial of the at least one filter medium in a concentration rangingfrom 0.01% to 5% by mass of the at least one filter medium. In someembodiments, after the step of increasing the NO_(x) removal efficiency,ABS deposits are disposed on the catalyst material of the at least onefilter medium in a concentration ranging from 0.01% to 1% by mass of theat least one filter medium. In some embodiments, after the step ofincreasing the NO_(x) removal efficiency, ABS deposits are disposed onthe catalyst material of the at least one filter medium in aconcentration ranging from 0.01% to 0.1% by mass of the at least onefilter medium.

In some embodiments, after the step of increasing the NO_(x) removalefficiency, ABS deposits are disposed on the catalyst material of the atleast one filter medium in a concentration ranging from 0.1% to 98% bymass of the at least one filter medium. In some embodiments, after thestep of increasing the NO_(x) removal efficiency, ABS deposits aredisposed on the catalyst material of the at least one filter medium in aconcentration ranging from 1% to 98% by mass of the at least one filtermedium. In some embodiments, after the step of increasing the NO_(x)removal efficiency, ABS deposits are disposed on the catalyst materialof the at least one filter medium in a concentration ranging from 5% to98% by mass of the at least one filter medium. In some embodiments,after the step of increasing the NO_(x) removal efficiency, ABS depositsare disposed on the catalyst material of the at least one filter mediumin a concentration ranging from 10% to 98% by mass of the at least onefilter medium. In some embodiments, after the step of increasing theNO_(x) removal efficiency, ABS deposits are disposed on the catalystmaterial of the at least one filter medium in a concentration rangingfrom 20% to 98% by mass of the at least one filter medium. In someembodiments, after the step of increasing the NO_(x) removal efficiency,ABS deposits are disposed on the catalyst material of the at least onefilter medium in a concentration ranging from 50% to 98% by mass of theat least one filter medium. In some embodiments after the step ofincreasing the NO_(x) removal efficiency, ABS deposits are disposed onthe catalyst material of the at least one filter medium in aconcentration ranging from 90% to 98% by mass of the at least one filtermedium.

In some embodiments, after the increasing step, ABS deposits aredisposed on the catalyst material of the at least one filter medium in aconcentration ranging from 0.1% to 90% by mass of the at least onefilter medium. In some embodiments, after the step of increasing theNO_(x) removal efficiency, ABS deposits are disposed on the catalystmaterial of the at least one filter medium in a concentration rangingfrom 1% to 50% by mass of the at least one filter medium. In someembodiments, after the step of increasing the NO_(x) removal efficiency,ABS deposits are disposed on the catalyst material of the at least onefilter medium in a concentration ranging from 5% to 20% by mass of theat least one filter medium.

Some embodiments of the present disclosure relate to a method ofcleaning a flue gas stream. As used herein, “cleaning a flue gas stream”means that after “cleaning a flue gas stream” at least one component(such as, but not limited to, NO, NO₂, or a combination thereof) of theflue gas stream is present at a lower concentration as compared to aconcentration of the at least one component prior to “cleaning the fluegas stream.” As described herein, “cleaning a flue gas stream” is notnecessarily mutually exclusive with “regenerating at least one filtermedium” because, in some embodiments, at least one filter medium, priorto regeneration, may still “clean a flue gas stream,” at a lowerefficiency as compared to the “at least one filter medium,” afterregeneration.

In some embodiments, at least one filter medium may be regeneratedduring the cleaning of the flue gas stream. In some embodiments, atleast one filter medium may be regenerated before the cleaning of theflue gas stream. In some embodiments, at least one filter medium may beregenerated after the cleaning of the flue gas stream. In someembodiments, a method may comprise switching between configurations of“cleaning a flue gas stream” and “regenerating at least one filtermedium.” In some embodiments, at least one step, component, orcombination thereof from a method of “cleaning a flue gas stream” may beused in a method of “regenerating at least one filter medium” or viceversa.

In some embodiments, the method of cleaning the flue gas stream maycomprise flowing a flue gas stream through a filter medium as describedherein, (i.e., transverse to a cross-section of a filter medium, suchthat the flue gas stream passes through the cross section of the atleast one filter medium).

In some embodiments of the method of cleaning the flue gas stream, theflue gas stream may comprise NO_(x) compounds. In some embodiments, theNO_(x) compounds may comprise Nitric Oxide (NO), and Nitrogen Dioxide(NO₂). In some embodiments, the flue gas stream may further compriseSulfur Dioxide (SO₂) and Ammonia (NH₃).

In some embodiments, the SO₂, NH₃, and NO_(x) compounds are present inan amount of at least 1 mg/m³ based on a total volume of the flue gasstream. In some embodiments, the SO₂, NH₃, and NO_(x) compounds arepresent in an amount of at least 2 mg/m³ based on a total volume of theflue gas stream. In some embodiments, the SO₂, NH₃, and NO_(x) compoundsare present in an amount of at least 5 mg/m³ based on a total volume ofthe flue gas stream. In some embodiments, the SO₂, NH₃, and NO_(x)compounds are present in an amount of at least 10 mg/m³ based on a totalvolume of the flue gas stream. In some embodiments, the SO₂, NH₃, andNO_(x) compounds are present in an amount of at least 25 mg/m³ based ona total volume of the flue gas stream. In some embodiments, the SO₂,NH₃, and NO_(x) compounds are present in an amount of at least 50 mg/m³based on a total volume of the flue gas stream. In some embodiments, theSO₂, NH₃, and NO_(x) compounds are present in an amount of at least 100mg/m³ based on a total volume of the flue gas stream.

In some embodiments of the method of cleaning the flue gas stream, themethod may include maintaining a constant NO_(x) removal efficiency ofthe at least one filter medium. As used herein “a constant NO_(x)removal efficiency” means that a NO_(x) removal efficiency of the atleast one filter medium does not vary by more than a predeterminedamount.

In some embodiments of the method of cleaning the flue gas stream, themethod may include maintaining NO_(x) removal efficiency of the at leastone filter medium that does not vary by more than ±0.1%. In someembodiments of the method of cleaning the flue gas stream, the methodmay include maintaining NO_(x) removal efficiency of the at least onefilter medium that does not vary by more than ±0.5%. In some embodimentsof the method of cleaning the flue gas stream, the method may includemaintaining NO_(x) removal efficiency of the at least one filter mediumthat does not vary by more than ±1%. In some embodiments of the methodof cleaning the flue gas stream, the method may include maintainingNO_(x) removal efficiency of the at least one filter medium that doesnot vary by more than ±2%. In some embodiments of the method of cleaningthe flue gas stream, the method may include maintaining NO_(x) removalefficiency of the at least one filter medium that does not vary by morethan ±3%. In some embodiments of the method of cleaning the flue gasstream, the method may include maintaining NO_(x) removal efficiency ofthe at least one filter medium that does not vary by more than ±4%. Insome embodiments of the method of cleaning the flue gas stream, themethod may include maintaining NO_(x) removal efficiency of the at leastone filter medium that does not vary by more than ±5%.

In some embodiments, maintaining a constant NO_(x) removal efficiency ofthe at least one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 2%to 99% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 5%to 99% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from10% to 99% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from25% to 99% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from50% to 99% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from75% to 99% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from95% to 99% of a total concentration of the NO_(x) compounds.

In some embodiments, maintaining a constant NO_(x) removal efficiency ofthe at least one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 2%to 95% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 2%to 75% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 2%to 50% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 2%to 25% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 2%to 10% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 2%to 5% of a total concentration of the NO_(x) compounds.

In some embodiments, maintaining a constant NO_(x) removal efficiency ofthe at least one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from 5%to 95% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium in a range from 10%to 75% of a total concentration of the NO_(x) compounds. In someembodiments, maintaining a constant NO_(x) removal efficiency of the atleast one filter medium comprises providing an NO₂ concentration,measured from the upstream side of the filter medium, in a range from25% to 50% of a total concentration of the NO_(x) compounds.

In some embodiments, maintaining a constant NO_(x) removal efficiency ofthe at least one filter medium may include controlling an NO₂concentration, measured from the downstream side of the filter medium,to a range of from 0.0001% to 0.5% of the concentration of the flue gasstream. In some embodiments, maintaining a constant NO_(x) removalefficiency of the at least one filter medium may include controlling anNO₂ concentration, measured from the downstream side of the filtermedium, to a range of from 0.001% to 0.5% of the concentration of theflue gas stream. In some embodiments, maintaining a constant NO_(x)removal efficiency of the at least one filter medium may includecontrolling an NO₂ concentration, measured from the downstream side ofthe filter medium, to a range of from 0.01% to 0.5% of the concentrationof the flue gas stream. In some embodiments, maintaining a constantNO_(x) removal efficiency of the at least one filter medium may includecontrolling an NO₂ concentration, measured from the downstream side ofthe filter medium, to a range of from 0.1% to 0.5% of the concentrationof the flue gas stream.

In some embodiments, maintaining a constant NO_(x) removal efficiency ofthe at least one filter medium may include controlling an NO₂concentration, measured from the downstream side of the filter medium,to a range of from 0.0001% to 0.1% of the concentration of the flue gasstream. In some embodiments, maintaining a constant NO_(x) removalefficiency of the at least one filter medium may include controlling anNO₂ concentration, measured from the downstream side of the filtermedium, to a range of from 0.0001% to 0.01% of the concentration of theflue gas stream. In some embodiments, maintaining a constant NO_(x)removal efficiency of the at least one filter medium may includecontrolling an NO₂ concentration, measured from the downstream side ofthe filter medium, to a range of from 0.0001% to 0.001% of theconcentration of the flue gas stream.

In some embodiments, maintaining a constant NO_(x) removal efficiency ofthe at least one filter medium may include controlling an NO₂concentration, measured from the downstream side of the filter medium,to a range of from 0.001% to 0.1% of the concentration of the flue gasstream. In some embodiments, maintaining a constant NO_(x) removalefficiency of the at least one filter medium may include controlling anNO₂ concentration, measured from the downstream side of the filtermedium, to a range of from 0.01% to 0.1% of the concentration of theflue gas stream.

In some embodiments NO_(x) efficiency is maintained in an amount of atleast 70% of an initial NO_(x) efficiency. In some embodiments NO_(x)efficiency is maintained in an amount of at least 75% of an initialNO_(x) efficiency. In some embodiments NO_(x) efficiency is maintainedin an amount of at least 80% of an initial NO_(x) efficiency. In someembodiments NO_(x) efficiency is maintained in an amount of at least 85%of an initial NO_(x) efficiency. In some embodiments NO_(x) efficiencyis maintained in an amount of at least 90% of an initial NO_(x)efficiency. In some embodiments NO_(x) efficiency is maintained in anamount of at least 95% of an initial NO_(x) efficiency. In someembodiments NO_(x) efficiency is maintained in an amount of at least 99%of an initial NO_(x) efficiency.

In some embodiments, the NO_(x) removal efficiency of the at least onefilter medium is maintained in a range of 70% to 99% of the initialNO_(x) efficiency. In some embodiments, the NO_(x) removal efficiency ofthe at least one filter medium is maintained in a range of 75% to 99% ofthe initial NO_(x) efficiency. In some embodiments, the NO_(x) removalefficiency of the at least one filter medium is maintained in a range of80% to 99% of the initial NO_(x) efficiency. In some embodiments, theNO_(x) removal efficiency of the at least one filter medium ismaintained in a range of 85% to 99% of the initial NO_(x) efficiency. Insome embodiments, the NO_(x) removal efficiency of the at least onefilter medium is maintained in a range of 90% to 99% of the initialNO_(x) efficiency. In some embodiments, the NO_(x) removal efficiency ofthe at least one filter medium is maintained in a range of 95% to 99% ofthe initial NO_(x) efficiency.

In some embodiments, the NO_(x) removal efficiency of the at least onefilter medium is maintained in a range of 70% to 95% of the initialNO_(x) efficiency. In some embodiments, the NO_(x) removal efficiency ofthe at least one filter medium is maintained in a range of 70% to 90% ofthe initial NO_(x) efficiency. In some embodiments, the NO_(x) removalefficiency of the at least one filter medium is maintained in a range of70% to 85% of the initial NO_(x) efficiency. In some embodiments, theNO_(x) removal efficiency of the at least one filter medium ismaintained in a range of 70% to 80% of the initial NO_(x) efficiency. Insome embodiments, the NO_(x) removal efficiency of the at least onefilter medium is maintained in a range of 70% to 75% of the initialNO_(x) efficiency.

In some embodiments, the NO_(x) removal efficiency of the at least onefilter medium is maintained in a range of 75% to 95% of the initialNO_(x) efficiency. In some embodiments, the NO_(x) removal efficiency ofthe at least one filter medium is maintained in a range of 80% to 90% ofthe initial NO_(x) efficiency.

In some embodiments, NO_(x) efficiency is maintained by increasing NO₂.In some embodiments, NO₂ is increased periodically. In some embodiments,NO₂ is increased continuously. In some embodiments, the periodicaddition of NO₂ occurs at constant time intervals. In some embodiments,the periodic addition of NO₂ occurs at variable time intervals. In someembodiments, the periodic addition of NO₂ occurs at random timeintervals.

In some embodiments, the periodic addition of NO₂ comprises increasingNO₂ every 1 to 40,000 hours. In some embodiments, the periodic additionof NO₂ comprises increasing NO₂ every 10 to 40,000 hours. In someembodiments, the periodic addition of NO₂ comprises increasing NO₂ every100 to 40,000 hours. In some embodiments, the periodic addition of NO₂comprises increasing NO₂ every 1,000 to 40,000 hours. In someembodiments, the periodic addition of NO₂ comprises increasing NO₂ every5,000 to 40,000 hours. In some embodiments, the periodic addition of NO₂comprises increasing NO₂ every 10,000 to 40,000 hours. In someembodiments, the periodic addition of NO₂ comprises increasing NO₂ every20,000 to 40,000 hours. In some embodiments, the periodic addition ofNO₂ comprises increasing NO₂ every 30,000 to 40,000 hours.

In some embodiments, the periodic addition of NO₂ comprises increasingNO₂ every 1 to 30,000 hours. In some embodiments, the periodic additionof NO₂ comprises increasing NO₂ every 1 to 20,000 hours. In someembodiments, the periodic addition of NO₂ comprises increasing NO₂ every1 to 10,000 hours. In some embodiments, the periodic addition of NO₂comprises increasing NO₂ every 1 to 5,000 hours. In some embodiments,the periodic addition of NO₂ comprises increasing NO₂ every 1 to 1,000hours. In some embodiments, the periodic addition of NO₂ comprisesincreasing NO₂ every 1 to 100 hours. In some embodiments, the periodicaddition of NO₂ comprises increasing NO₂ every 1 to 10 hours.

In some embodiments, the periodic addition of NO₂ comprises increasingNO₂ every 10 to 30,000 hours. In some embodiments, the periodic additionof NO₂ comprises increasing NO₂ every 100 to 20,000 hours. In someembodiments, the periodic addition of NO₂ comprises increasing NO₂ every1,000 to 5,000 hours.

In some embodiments, the continuous addition of the NO₂ comprisesproviding NO₂ at a flow rate of 2% to 99% of a total flow rate of theupstream NO_(x) compounds. In some embodiments, the continuous additionof the NO₂ comprises providing NO₂ at a flow rate of 5% to 99% of atotal flow rate of the upstream NO_(x) compounds. In some embodiments,the continuous addition of the NO₂ comprises providing NO₂ at a flowrate of 10% to 99% of a total flow rate of the upstream NO_(x)compounds. In some embodiments, the continuous addition of the NO₂comprises providing NO₂ at a flow rate of 20% to 99% of a total flowrate of the upstream NO_(x) compounds. In some embodiments, thecontinuous addition of the NO₂ comprises providing NO₂ at a flow rate of30% to 99% of a total flow rate of the upstream NO_(x) compounds. Insome embodiments, the continuous addition of the NO₂ comprises providingNO₂ at a flow rate of 40% to 99% of a total flow rate of the upstreamNO_(x) compounds. In some embodiments, the continuous addition of theNO₂ comprises providing NO₂ at a flow rate of 50% to 99% of a total flowrate of the upstream NO_(x) compounds. In some embodiments, thecontinuous addition of the NO₂ comprises providing NO₂ at a flow rate of60% to 99% of a total flow rate of the upstream NO_(x) compounds. Insome embodiments, the continuous addition of the NO₂ comprises providingNO₂ at a flow rate of 70% to 99% of a total flow rate of the upstreamNO_(x) compounds. In some embodiments, the continuous addition of theNO₂ comprises providing NO₂ at a flow rate of 80% to 99% of a total flowrate of the upstream NO_(x) compounds. In some embodiments, thecontinuous addition of the NO₂ comprises providing NO₂ at a flow rate of95% to 99% of a total flow rate of the upstream NO_(x) compounds.

In some embodiments, the continuous addition of the NO₂ comprisesproviding NO₂ at a flow rate of 2% to 95% of a total flow rate of theupstream NO_(x) compounds. In some embodiments, the continuous additionof the NO₂ comprises providing NO₂ at a flow rate of 2% to 90% of atotal flow rate of the upstream NO_(x) compounds. In some embodiments,the continuous addition of the NO₂ comprises providing NO₂ at a flowrate of 2% to 80% of a total flow rate of the upstream NO_(x) compounds.In some embodiments, the continuous addition of the NO₂ comprisesproviding NO₂ at a flow rate of 2% to 70% of a total flow rate of theupstream NO_(x) compounds. In some embodiments, the continuous additionof the NO₂ comprises providing NO₂ at a flow rate of 2% to 60% of atotal flow rate of the upstream NO_(x) compounds. In some embodiments,the continuous addition of the NO₂ comprises providing NO₂ at a flowrate of 2% to 50% of a total flow rate of the upstream NO_(x) compounds.In some embodiments, the continuous addition of the NO₂ comprisesproviding NO₂ at a flow rate of 2% to 40% of a total flow rate of theupstream NO_(x) compounds. In some embodiments, the continuous additionof the NO₂ comprises providing NO₂ at a flow rate of 2% to 30% of atotal flow rate of the upstream NO_(x) compounds. In some embodiments,the continuous addition of the NO₂ comprises providing NO₂ at a flowrate of 2% to 20% of a total flow rate of the upstream NO_(x) compounds.In some embodiments, the continuous addition of the NO₂ comprisesproviding NO₂ at a flow rate of 2% to 10% of a total flow rate of theupstream NO_(x) compounds. In some embodiments, the continuous additionof the NO₂ comprises providing NO₂ at a flow rate of 2% to 5% of a totalflow rate of the upstream NO_(x) compounds.

In some embodiments, the continuous addition of the NO₂ comprisesproviding NO₂ at a flow rate of 5% to 95% of a total flow rate of theupstream NO_(x) compounds. In some embodiments, the continuous additionof the NO₂ comprises providing NO₂ at a flow rate of 10% to 90% of atotal flow rate of the upstream NO_(x) compounds. In some embodiments,the continuous addition of the NO₂ comprises providing NO₂ at a flowrate of 20% to 80% of a total flow rate of the upstream NO_(x)compounds. In some embodiments, the continuous addition of the NO₂comprises providing NO₂ at a flow rate of 30% to 70% of a total flowrate of the upstream NO_(x) compounds. In some embodiments, thecontinuous addition of the NO₂ comprises providing NO₂ at a flow rate of40% to 60% of a total flow rate of the upstream NO_(x) compounds.

FIGS. 1A-1D depict embodiments of an exemplary filter medium accordingto the present disclosure.

Referring to FIG. 1A, at least one filter medium 101 may be housed in atleast one filter bag 100. A flue gas stream 102 may flow through the atleast one filter medium 101 by passing through cross section A. Once theflue gas stream 102 flows through the at least one filter medium 101,the flue gas stream 102 may flow by the at least one filter bag, asindicated by the vertically oriented arrows.

FIG. 1B depicts an exemplary filter medium 101 according to someembodiments of the present disclosure. As shown in FIG. 1B, a flue gasstream 102, which may comprise NO_(x) compounds and solid particulates107, may flow through cross section A from an upstream side 103 of thefilter medium 101 to a downstream side 104 of the filter medium. Whilenot shown, the upstream side 103 of the filter medium 101 may, in someembodiments, correspond to an outside of a filter bag, such as filterbag 100. Likewise, downstream side 104 of the filter medium 101 maycorrespond to an inside of a filter bag, such as filter bag 100. In someembodiments, filter medium 101 may include at least one protectivemembrane 106 and one or more felt batts 108 on at least one of: theupstream side 103 the of the filter medium 101, the downstream side 104the of the filter medium 101, or any combination thereof. In someembodiments, the one or more felt batts 108 may be positioned on aporous catalytic film 105. In some embodiments, the combination of theone or more felt batts 108 and the porous catalytic film 105 may bereferred to as a porous catalytic layer (not shown in FIG. 1B).

FIG. 1C depicts a non-limiting exemplary embodiment of the porouscatalytic film 105. As shown, porous catalytic film 105 may includecatalyst particles 109 on at least one surface of the porous catalyticfilm 105. ABS deposits 110 may be disposed on the surface of thecatalyst particles 109.

FIG. 1D depicts an additional non-limiting exemplary embodiment of afilter medium 101. As shown, filter medium 101 may comprise a porouscatalytic layer 111. In some non-limiting embodiments, filter medium 101may take the form of a filter bag. In some embodiments the porouscatalytic layer 111 may be coated with a catalyst material (not shown inFIG. 1D) such as catalyst particles. In some embodiments, the catalystmaterial may be attached to the porous catalytic layer 111 by one ormore adhesives described herein (not shown). In some embodiments, thefilter medium 101 may include a porous protective membrane 106.

At least some non-limiting aspects of the present disclosure will now bedescribed with reference to the following numbered embodimentshereinafter designated as [E1, E2, E3, E4 . . . ]:

-   -   E1. A method comprising:        -   providing at least one filter medium;            -   wherein the at least one filter medium comprises:                -   at least one catalyst material; and                -   ammonium bisulfate (ABS) deposits, ammonium sulfate                    (AS) deposits, or any combination thereof;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂); and        -   increasing NO_(x) removal efficiency of the at least one            filter medium;            -   wherein the increasing of the NO_(x) removal efficiency                of the at least one filter medium comprises increasing                an upstream NO₂ concentration to a range from 2% to 99%                of a total concentration of the upstream NO_(x)                compounds,                wherein the method regenerates the at least one filter                medium.    -   E2. A method comprising:        -   providing at least one filter medium;            -   wherein the at least one filter medium comprises:                -   at least one catalyst material; and                -   ammonium bisulfate (ABS), ammonium sulfate (AS), or                    any combination thereof;        -   flowing a flue gas stream through or by the at least one            filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);        -   increasing NO_(x) removal efficiency of the at least one            filter medium;            -   wherein the increasing of the NO_(x) removal efficiency                of the at least one filter medium comprises increasing                an upstream NO₂ concentration to a range from 2% to 99%                of a total concentration of the upstream NO_(x)                compounds;            -   wherein the increasing of the NO_(x) removal efficiency                of the at least one filter medium further comprises                adding ammonia (NH₃) in a concentration ranging from                0.0001% to 0.5% of the concentration of the flue gas                stream;                wherein the method regenerates the at least one filter                medium.    -   E3. The method of any of the preceding embodiments or any        combination thereof, wherein the temperature of the flue gas        stream ranges from 160° C. to 280° C. during the flowing step.    -   E4. The method of any of the preceding embodiments, or any        combination thereof, wherein the flue gas stream further        comprises at least one of Oxygen (O₂), Water (H₂O), Nitrogen        (N₂), Carbon Monoxide (CO), Sulfur Dioxide (SO₂), Sulfur        Trioxide (SO₃), one or more hydrocarbons, or any combination        thereof.    -   E5. The method of embodiment 2, wherein the flue gas stream is        flowed transverse to a cross-section of the at least one filter        medium, such that the flue gas stream passes through the cross        section of the at least one filter medium.    -   E6. The method of embodiment 2, wherein the flue gas stream is        not flowed transverse to a cross-section of the at least one        filter medium, such that the flue gas stream does not pass        through the cross section of the at least one filter medium.    -   E7. The method of embodiment 1, 3-5, or any combination thereof,        wherein the flue gas stream is flowed perpendicular to a        cross-section of the at least one filter medium.    -   E8. The method of embodiment 6, wherein the flue gas stream is        flowed parallel to a cross-section of the at least one filter        medium.    -   E9. The method of embodiments 1, 3-5, 7, or any combination        thereof, wherein the at least one filter medium is disposed        within at least one filter bag, wherein the at least one filter        bag is housed within at least one filter bag housing, and        wherein the at least one catalyst material is in the form of        catalyst particles.    -   E10. The method of any of embodiments 1, 3-5, 7, 9, or any        combination thereof, wherein the at least one filter medium        comprises a porous protective layer and a porous catalytic        layer, wherein the porous catalytic layer comprises the at least        one catalyst material.    -   E11. The method of embodiment 10, wherein the porous protective        layer comprises a microporous layer, wherein the microporous        layer comprises an expanded polytetrafluoroethylene (ePTFE)        membrane.    -   E12. The method of any of the preceding embodiments wherein the        at least one catalyst material is adhered to the filter medium        by at least one adhesive.    -   E13. The method of embodiment 12, wherein the at least one        adhesive is chosen from polytetrafluoroethylene (PTFE),        fluorinated ethylene propylene (FEP), high molecular weight        polyethylene (HMWPE), high molecular weight polypropylene        (HMWPP), perfluoroalkoxy alkane (PFA), polyvinylidene fluoride        (PVDF), vinylidene fluoride (THV), chlorofluoroethylene (CFE),        or any combination thereof.    -   E14. The method of embodiments, 9-10, 12, or any combination        thereof, wherein the porous catalytic layer comprises at least        one polymeric substrate.    -   E15. The method of embodiment 14, wherein the at least one        polymeric substrate comprises a least one of:        polytetrafluorethylene, poly(ethylene-co-tetrafluoroethylene),        ultra-high molecular weight polyethylene, polyparaxylylene,        polylactic acid, polyimide, polyamide, polyaramid, polyphenylene        sulfide, fiberglass, or any combination thereof.    -   E16. The method of embodiments, 9-10, 12, wherein the porous        catalytic layer includes at least one ceramic substrate.    -   E17. The method of embodiment 16, wherein the at least one        ceramic substrate comprises ceramic fibers, wherein the ceramic        fibers comprise, alkali metal silicates, alkaline earth metal        silicates, aluminosilicates, or any combination thereof.    -   E18. The method of embodiments 9-10 or any combination thereof,        wherein the porous catalytic layer is in the form of a layered        assembly comprising a porous catalytic film and one or more felt        batts, wherein the one or more felt batts are positioned on at        least one side of the porous catalytic film.    -   E19. The method of embodiment 18, wherein the one or more felt        batts comprise at least one of: a polytetrafluoroethylene (PTFE)        felt, a PTFE fleece, an expanded polytetrafluoroethylene (ePTFE)        felt, an ePTFE fleece, a woven fluoropolymer staple fiber, a        nonwoven fluoropolymer staple fiber, or any combination thereof.    -   E20. The method of embodiment 18, 19, or any combination        thereof, wherein the porous catalytic film comprises an expanded        polytetrafluoroethylene (ePTFE) membrane.    -   E21. The method of embodiments 10, 18-19, or any combination        thereof, wherein the catalyst particles are enmeshed within the        porous catalytic layer.    -   E22. The method of embodiments 10, 18-20, or any combination        thereof, wherein the porous catalytic layer comprises a least        one of: polytetrafluorethylene (PTFE),        poly(ethylene-co-tetrafluoroethylene) (ETFE), ultra-high        molecular weight polyethylene (UHMWPE), polyparaxylylene (PPX),        polylactic acid, polyimide, polyamide, polyaramid, polyphenylene        sulfide, fiberglass, or any combination thereof.    -   E23. The method of embodiments 1-8, or any combination thereof,        wherein the at least one filter medium is in the form of a        ceramic candle, wherein the ceramic candle comprises at least        one ceramic material.    -   E24. The method of embodiment 16, 17, 22, or any combination        thereof, wherein the temperature of the flue gas stream ranges        from 170° C. to 450° C. during the flowing step.    -   E25. The method of embodiment 23, 24, or any combination        thereof, wherein the least one ceramic material is chosen from:        silica-aluminate, calcium-magnesium-silicate, calcium-silicate        fibers, or any combination thereof.    -   E26. The method of embodiments 24-25, or any combination        thereof, wherein the at least one catalyst is in the form of        catalyst particles, wherein the catalyst particles form a        coating on the at least one ceramic material.    -   E27. The method of any of the preceding embodiments or any        combination thereof, wherein the at least one catalyst material        comprises at least one of: Vanadium Monoxide (VO), Vanadium        Trioxide (V₂O₃), Vanadium Dioxide (VO₂), Vanadium Pentoxide        (V₂O₅), Tungsten Trioxide (WO₃), Molybdenum Trioxide (MoO₃),        Titanium Dioxide (TiO₂), Silicon Dioxide (SiO₂), Aluminum        Trioxide (Al₂O₃), Manganese Oxide (MnO₂), zeolites, or any        combination thereof.    -   E28. The method of any of the preceding embodiments or any        combination thereof, wherein ABS deposits are disposed on the        catalyst material of the at least one filter medium in a        concentration ranging from 0.01% to 99% by mass of the at least        one filter medium during the providing step.    -   E29. The method of any of the preceding embodiments or any        combination thereof, wherein ABS deposits are disposed on the        catalyst material of the at least one filter medium in a        concentration ranging from 0.01% to 98% by mass of the at least        one filter medium after the increasing step.    -   E30. The method of any of the preceding embodiments or any        combination thereof, wherein the concentration of NO₂ is        increased by introducing at least one oxidizing agent to the        flue gas stream.    -   E31. The method of embodiment 21, wherein the at least one        oxidizing agent is chosen from: hydrogen peroxide (H₂O₂), ozone        (O₃), hydroxyl radical, or any combination thereof.    -   E32. The method of embodiment 21, wherein the concentration of        NO₂ is increased by introducing additional NO₂ into the flue gas        stream.    -   E33. The method of embodiments 1, 3, 4, 7, 9-32, or any        combination thereof further comprising adding NH₃ in a        concentration ranging from 0.0001% to 0.5% of the concentration        of the flue gas stream.    -   E34. The method of any of the preceding embodiments or any        combination thereof, wherein the NO_(x) removal efficiency of        the at least one filter medium is at least 0.5% higher after the        increasing step than during the providing step.    -   E35. The method of embodiment 2, wherein the at least one filter        medium is in the form of at least one of: a filter bag, a        honeycomb structure, a monolith structure or any combination        thereof.    -   E36. The method of any of the preceding embodiments or any        combination thereof, wherein the increasing of the NO_(x)        removal efficiency comprises removing at least some of the ABS        deposits, the AS deposits, or any combination thereof, from the        at least one filter medium.    -   E37. A method comprising:        -   providing at least one filter medium            -   wherein the at least one filter medium comprises at                least one catalyst material;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium from an upstream side of the filter medium to            a downstream side of the filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);                -   Sulfur Dioxide (SO₂); and                -   Ammonia (NH₃);        -   maintaining a constant NO_(x) removal efficiency of the at            least one filter medium;            -   wherein the maintaining a constant NO_(x) removal                efficiency of the at least one filter medium comprises:                -   providing NO₂ concentration, measured from the                    upstream side of the filter medium, in a range from                    2% to 99% of a total concentration of the NO_(x)                    compounds; and                -   controlling NO₂ concentration, measured from the                    downstream side of the filter medium, to a range of                    from 0.0001% to 0.5% of the concentration of the                    flue gas stream                    wherein the method cleans the flue gas stream.    -   E38. The method of embodiment 37, wherein the SO₂, NH₃, and        NO_(x) compounds are present in an amount of at least 1 mg/m³        based on a total volume of the flue gas stream.    -   E39. A method comprising:        -   providing at least one filter medium            -   wherein the at least one filter medium comprises at                least one catalyst material;        -   flowing a flue gas stream by a cross-section of the at least            one filter medium, such that the flue gas stream is flowed            parallel to a cross-section of the at least one filter            medium from an upstream side of the filter medium to a            downstream side of the filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);                -   Sulfur Dioxide (SO₂); and                -   Ammonia (NH₃);        -   maintaining a constant NO_(x) removal efficiency of the at            least one filter medium;            -   wherein the maintaining a constant NO_(x) removal                efficiency of the at least one filter medium comprises:                -   providing NO₂ concentration, measured from the                    upstream side of the filter medium, in a range from                    2% to 99% of a total concentration of the NO_(x)                    compounds; and                -   controlling NO₂ concentration, measured from the                    downstream side of the filter medium, to a range of                    from 0.0001% to 0.5% of the concentration of the                    flue gas stream                    wherein the method cleans the flue gas stream.    -   E40. The method of embodiment 39, wherein the SO₂, NH₃, and        NO_(x) compounds are present in an amount of at least 1 mg/m³        based on a total volume of the flue gas stream.    -   E41. The method of embodiment 39, wherein the at least one        filter medium is in the form of at least one of: a honeycomb        structure, a monolith structure or any combination thereof.    -   E42. A filter medium comprising:        -   an upstream side;        -   a downstream side;        -   at least one catalyst material; and        -   ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)            deposits, or any combination thereof;    -   wherein the filter medium is configured to receive a flow of a        flue gas stream transverse to a cross-section of the filter        medium, such that the flue gas stream passes through the cross        section of the at least one filter medium from the upstream side        of the filter medium to the downstream side of the filter        medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂); and    -   wherein the at least one filter medium is configured to increase        an NO_(x) removal efficiency of the at least one filter medium        upon an increase of to a range from 2% to 99% of a total        concentration of the upstream NO_(x) compounds.    -   E43. The filter medium of embodiment 42, wherein, the at least        one filter medium is configured to further increase an NO_(x)        removal efficiency of the at least one filter medium when        ammonia (NH₃) is added in a concentration ranging from 0.0001%        to 0.5% of the concentration of the flue gas stream.    -   E44. A filter medium comprising:        -   an upstream side;        -   a downstream side; and        -   at least one catalyst material;    -   wherein the filter medium is configured to receive a flow of a        flue gas stream transverse to a cross-section of the filter        medium, such that the flue gas stream passes through the cross        section of the at least one filter medium from the upstream side        of the filter medium to the downstream side of the filter        medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂);            -   Sulfur Dioxide (SO₂); and            -   Ammonia (NH₃);    -   wherein the at least one filter medium is configured to maintain        a constant NO_(x) removal efficiency of the at least one filter        medium when:        -   an NO₂ concentration, measured from the upstream side of the            filter medium, is provided in a range from 2% to 99% of a            total concentration of the NO_(x) compounds; and        -   an NO₂ concentration, measured from the downstream side of            the filter medium, is controlled to a range of from 0.0001%            to 0.5% of the total concentration of the flue gas stream.    -   E45. A filter medium comprising:        -   an upstream side;        -   a downstream side; and        -   at least one catalyst material;    -   wherein the filter medium is configured to receive a flow of a        flue gas stream by a cross-section of the filter medium, such        that the flue gas stream is not flowed transverse to a        cross-section of the at least one filter medium from an upstream        side of the filter medium to a downstream side of the filter        medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂);            -   Sulfur Dioxide (SO₂); and            -   Ammonia (NH₃);    -   wherein the at least one filter medium is configured to maintain        a constant NO_(x) removal efficiency of the at least one filter        medium when:        -   an NO₂ concentration, measured from the upstream side of the            filter medium, is provided in a range from 2% to 99% of a            total concentration of the NO_(x) compounds; and        -   an NO₂ concentration, measured from the downstream side of            the filter medium, is controlled to a range of from 0.0001%            to 0.5% of the total concentration of the flue gas stream.    -   E46. A system comprising:        -   at least one filter medium,            -   wherein the at least one filter medium comprises:                -   an upstream side;                -   a downstream side;                -   at least one catalyst material; and                -   ammonium bisulfate (ABS) deposits, ammonium sulfate                    (AS) deposits, or any combination thereof;        -   at least one filter bag,            -   wherein the at least one filter medium is disposed                within the at least one filter bag; and        -   at least one filter bag housing,            -   wherein the at least one filter bag is disposed within                the at least one filter bag housing;            -   wherein the at least one filter bag housing is                configured to receive a flow of a flue gas stream                transverse to a cross-section of the at least one filter                medium, such that the flue gas stream passes through the                cross section of the at least one filter medium from the                upstream side of the at least one filter medium to the                downstream side of the at least one filter medium,                -   wherein the flue gas stream comprises:                -    NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂); and    -   wherein the system is configured to increase an NO_(x) removal        efficiency of the at least one filter medium when an upstream        NO₂ concentration is increased to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds.    -   E47. A filter bag housing comprising:        -   a filter medium,            -   wherein the filter medium comprises:                -   an upstream side;                -   a downstream side;                -   at least one catalyst material; and                -   ammonium bisulfate (ABS) deposits, ammonium sulfate                    (AS) deposits, or any combination thereof; and        -   a filter bag,            -   wherein the filter medium is disposed within the filter                bag;            -   wherein the filter bag is disposed within the filter bag                housing;        -   wherein the filter bag housing is configured to receive a            flow of a flue gas stream transverse to a cross-section of            the filter medium, such that the flue gas stream passes            through the cross section of the at least one filter medium            from the upstream side of the filter medium to the            downstream side of the filter medium,        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:            -   Nitric Oxide (NO), and            -   Nitrogen Dioxide (NO₂); and    -   wherein the filter bag housing is configured to increase an        NO_(x) removal efficiency of the at least one filter medium when        an upstream NO₂ concentration is increased to a range from 2% to        99% of a total concentration of the upstream NO_(x) compounds.    -   E48. The method of embodiments 1 to 41 or any combination        thereof, wherein NO₂ is added to the flue gas stream        periodically, so as to maintain the NO_(x) removal efficiency in        an amount of at least 70% of an initial NO_(x) efficiency.    -   E49. The method of embodiment 48, wherein the periodic addition        of NO₂ comprises increasing NO₂ every 1 to 40,000 hours.    -   E50. The method of embodiment 48, 49, or any combination        thereof, wherein the periodic addition occurs at constant time        intervals.    -   E51. The method of embodiment 48, 49, or any combination        thereof, wherein the periodic addition occurs at variable time        intervals.    -   E52. The method of embodiment 51, wherein variable time        intervals are random time intervals.    -   E53. The method of embodiments 1 to 41 or any combination        thereof, wherein NO₂ is added to the flue gas stream        continuously, so as to maintain the NO_(x) removal efficiency in        an amount of at least 70% of an initial NO_(x) efficiency.    -   E54. The method of embodiment 53 wherein the continuous addition        of the NO₂ comprises providing NO₂ at a flow rate of 2% to 99%        of a total flow rate of the upstream NO_(x) compounds.    -   E55. A method comprising:        -   providing at least one filter medium            -   wherein the at least one filter medium comprises at                least one catalyst material;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium from an upstream side of the filter medium to            a downstream side of the filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);                -   Sulfur Dioxide (SO₂); and                -   Ammonia (NH₃);        -   maintaining an NO_(x) removal efficiency of the at least one            filter medium in an amount of at least 70% of an initial            NO_(x) efficiency by:            -   providing an NO₂ concentration, measured from the                upstream side of the filter medium, in a range from 2%                to 99% of a total concentration of the NO_(x) compounds;                and            -   controlling NO₂ concentration, measured from the                downstream side of the filter medium, to a range of from                0.0001% to 0.5% of the concentration of the flue gas                stream                wherein the method cleans the flue gas stream.    -   E56. The method of embodiment 55, wherein the NO_(x) removal        efficiency of the at least one filter medium is maintained in a        range of 70% to 99% of the initial NO_(x) efficiency.    -   E57. The method of embodiment 55, 60, or any combination        thereof, wherein during the maintaining of the NO_(x) removal        efficiency, the NO₂ concentration is increased periodically.    -   E58. The method of embodiment 57, wherein the periodic increase        of NO₂ comprises increasing NO₂ every 1 to 40,000 hours.    -   E59. The method of embodiment 57, 58, or any combination        thereof, wherein the periodic increase occurs at constant time        intervals.    -   E60. The method of embodiment 57, 58, or any combination        thereof, wherein the periodic increase occurs at variable time        intervals.    -   E61. The method of embodiment 60, wherein variable time        intervals are random time intervals.    -   E62. The method of any of embodiments 55, 60, or any combination        thereof, wherein during the providing of the NO₂ concentration,        the NO₂ concentration is provided continuously.    -   E63. The method of embodiment 62, wherein the continuous        providing of the NO₂ comprises providing NO₂ at a flow rate of        2% to 99% of a total flow rate of the upstream NO_(x) compounds.    -   E64. A method comprising:        -   providing at least one filter medium;            -   wherein the at least one filter medium comprises:                -   at least one catalyst material; and                -   ammonium bisulfate (ABS) deposits, ammonium sulfate                    (AS) deposits, or any combination thereof;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium,        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂); and    -   increasing NO_(x) removal efficiency of the at least one filter        medium;        -   wherein the increasing of the NO_(x) removal efficiency of            the at least one filter medium comprises increasing an            upstream NO₂ concentration to a range from 2% to 99% of a            total concentration of the upstream NO_(x) compounds,            wherein increasing the upstream NO₂ concentration to a range            from 2% to 99% of a total concentration of the upstream            NO_(x) compounds comprises introducing additional NO₂ into            the flue gas stream; and            wherein the method regenerates the at least one filter            medium.    -   E65. The method of embodiment 64, wherein a temperature of the        flue gas stream ranges from 160° C. to 280° C. during the        flowing step.    -   E66. The method of embodiment 64 or embodiment 65, wherein the        flue gas stream further comprises Oxygen (O₂), Water (H₂O),        Nitrogen (N₂), Carbon Monoxide (CO), Sulfur Dioxide (SO₂),        Sulfur Trioxide (SO₃), one or more hydrocarbons, or any        combination thereof.    -   E67. The method of any of embodiments 64 to 66, wherein flowing        the flue gas stream transverse to the cross-section of the at        least one filter medium comprises flowing the flue gas stream        perpendicular to the cross-section of the at least one filter        medium.    -   E68. The method of any of embodiments 64 to 67, wherein the at        least one filter medium is disposed within at least one filter        bag, wherein the at least one filter bag is housed within at        least one filter bag housing, and wherein the at least one        catalyst material is in the form of catalyst particles.    -   E69. The method of embodiment 68, wherein the at least one        filter medium comprises:        -   a porous protective layer; and        -   a porous catalytic layer, wherein the porous catalytic layer            comprises the catalyst particles.    -   E70. The method of embodiment 69, wherein the porous protective        layer of the at least one filter medium comprises a microporous        layer, wherein the microporous layer comprises an expanded        polytetrafluoroethylene (ePTFE) membrane.    -   E71. The method of embodiment 69 or embodiment 70, wherein the        porous catalytic layer of the at least one filter medium        comprises at least one polymeric substrate.    -   E72. The method of any of embodiments 69 to 71, wherein the        porous catalytic layer comprises at least one ceramic substrate.    -   E73. The method any of embodiments 69 to 72, wherein the porous        catalytic layer comprises polytetrafluorethylene (PTFE),        poly(ethylene-co-tetrafluoroethylene) (ETFE), ultra-high        molecular weight polyethylene (UHMWPE), polyparaxylylene (PPX),        polylactic acid, polyimide, polyamide, polyaramid, polyphenylene        sulfide, fiberglass, or any combination thereof.    -   E74. The method of any of embodiments 69 to 73, wherein the        catalyst particles are enmeshed within the porous catalytic        layer.    -   E75. The method of any of embodiments 69 to 74, wherein the        porous catalytic layer is in the form of a layered assembly        comprising:        -   a porous catalytic film; and        -   at least one felt batt, wherein the at least one felt batt            is positioned on at least one side of the porous catalytic            film.    -   E76. The method of embodiment 75, wherein the porous catalytic        film comprises an expanded polytetrafluoroethylene (ePTFE)        membrane.    -   E77. The method of embodiment 75 or 76, wherein the at least one        felt batt comprises: a polytetrafluoroethylene (PTFE) felt, a        PTFE fleece, an expanded polytetrafluoroethylene (ePTFE) felt,        an ePTFE fleece, a woven fluoropolymer staple fiber, a nonwoven        fluoropolymer staple fiber, or any combination thereof.    -   E78. The method of any of embodiments 64 to 77, wherein the at        least one catalyst material comprises at least one of: Vanadium        Monoxide (VO), Vanadium Trioxide (V₂O₃), Vanadium Dioxide (VO₂),        Vanadium Pentoxide (V₂O₅), Tungsten Trioxide (WO₃), Molybdenum        Trioxide (MoO₃), Titanium Dioxide (TiO₂), Silicon Dioxide        (SiO₂), Aluminum Trioxide (Al₂O₃), Manganese Oxide (MnO₂),        zeolites, or any combination thereof.    -   E79. The method of any of embodiments 64 to 75, wherein ABS        deposits are disposed on the catalyst material of the at least        one filter medium in a concentration ranging from 0.01% to 99%        by mass of the at least one filter medium during the providing        step.    -   E80. The method of any of embodiments 64 to 79, wherein, after        increasing the upstream NO₂ concentration to a range from 2% to        99% of a total concentration of the upstream NO_(x) compounds,        ABS deposits are disposed on the catalyst material of the at        least one filter medium in a concentration ranging from 0.01% to        98% by mass of the at least one filter medium.    -   E81. The method of any of embodiments 64 to 80, wherein the        increasing of the NO_(x) removal efficiency further comprises        removing at least some of the ABS deposits, the AS deposits, or        any combination thereof, from the at least one filter medium.    -   E82. A method comprising:        -   providing at least one filter medium            -   wherein the at least one filter medium comprises at                least one catalyst material;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium from an upstream side of the filter medium to            a downstream side of the filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);                -   Sulfur Dioxide (SO₂); and                -   Ammonia (NH₃);        -   maintaining a constant NO_(x) removal efficiency of the at            least one filter medium;            -   wherein the maintaining a constant NO_(x) removal                efficiency of the at least one filter medium comprises:                -   providing an NO₂ concentration, measured from the                    upstream side of the filter medium, in a range from                    2% to 99% of a total concentration of the NO_(x)                    compounds, wherein providing the NO₂ concentration,                    measured from the upstream side of the filter                    medium, in a range from 2% to 99% of a total                    concentration of the NO_(x) compounds comprises                    introducing additional NO₂ into the flue gas stream;                    and                -   controlling the NO₂ concentration, measured from the                    downstream side of the filter medium, to a range of                    from 0.0001% to 0.5% of the concentration of the                    flue gas stream;                    wherein the method cleans the flue gas stream.    -   E83. A system comprising:        -   at least one filter medium,            -   wherein the at least one filter medium comprises:                -   an upstream side;                -   a downstream side;                -   at least one catalyst material; and                -   ammonium bisulfate (ABS) deposits, ammonium sulfate                    (AS) deposits, or any combination thereof;        -   at least one filter bag,            -   wherein the at least one filter medium is disposed                within the at least one filter bag; and        -   at least one filter bag housing,            -   wherein the at least one filter bag is disposed within                the at least one filter bag housing;            -   wherein the at least one filter bag housing is                configured to receive a flow of a flue gas stream                transverse to a cross-section of the at least one filter                medium, such that the flue gas stream passes through the                cross section of the at least one filter medium from the                upstream side of the at least one filter medium to the                downstream side of the at least one filter medium,                -   wherein the flue gas stream comprises:                -    NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂); and        -   wherein the system is configured to increase a NO_(x)            removal efficiency of the at least one filter medium when an            upstream NO₂ concentration is increased to a range from 2%            to 99% of a total concentration of the upstream NO_(x)            compounds, and wherein the upstream NO₂ concentration is            increased to a range from 2% to 99% of a total concentration            of the upstream NO_(x) compounds by introducing additional            NO₂ into the flue gas stream.    -   E84. A method comprising:        -   providing at least one filter medium            -   wherein the at least one filter medium comprises at                least one catalyst material;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium from an upstream side of the filter medium to            a downstream side of the filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);                -   Sulfur Dioxide (SO₂); and                -   Ammonia (NH₃);        -   maintaining a NO_(x) removal efficiency of the at least one            filter medium in an amount of at least 70% of an initial            NO_(x) efficiency by:            -   providing an NO₂ concentration, measured from the                upstream side of the filter medium, in a range from 2%                to 99% of a total concentration of the NO_(x) compounds,                wherein providing the NO₂ concentration, measured from                the upstream side of the filter medium, in a range from                2% to 99% of a total concentration of the NO_(x)                compounds comprises introducing additional NO₂ into the                flue gas stream; and            -   controlling NO₂ concentration, measured from the                downstream side of the filter medium, to a range of from                0.0001% to 0.5% of the concentration of the flue gas                stream                wherein the method cleans the flue gas stream.    -   E85. The method of embodiment 84, wherein maintaining the NO_(x)        removal efficiency comprises maintaining the NO_(x) removal        efficiency in a range of 70% to 99% of the initial NO_(x)        efficiency.    -   E86. The method of embodiment 84 or 85, wherein maintaining of        the NO_(x) removal efficiency comprises increasing NO₂        concentration periodically.    -   E87. The method of embodiment 86, wherein increasing NO₂        concentration periodically comprises increasing NO₂ every 1 to        40,000 hours.    -   E88. The method of embodiment 86 or 87, wherein increasing NO₂        concentration periodically comprises increasing NO₂ at constant        time intervals.    -   E89. The method of embodiment 86 or 87, wherein increasing NO₂        concentration periodically comprises increasing NO₂ at variable        time intervals.    -   E90. The method of embodiment 89, wherein the variable time        intervals are random time intervals.    -   E91. The method of embodiment 84, wherein providing the NO₂        concentration comprises providing the NO₂ concentration        continuously.    -   E92. The method of embodiment 91, further comprising providing        the NO₂ concentration continuously comprises providing NO₂ at a        flow rate of 2% to 99% of a total flow rate of the upstream        NO_(x) compounds.    -   E93. A method comprising:        -   providing at least one filter medium;            -   wherein the at least one filter medium comprises:                -   at least one catalyst material; and                -   ammonium bisulfate (ABS) deposits, ammonium sulfate                    (AS) deposits, or any combination thereof;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium,            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂); and        -   increasing NO_(x) removal efficiency of the at least one            filter medium;            -   wherein the increasing of the NO_(x) removal efficiency                of the at least one filter medium comprises increasing                an upstream NO₂ concentration to a range from 2% to 99%                of a total concentration of the upstream NO_(x)                compounds, wherein increasing the upstream NO₂                concentration to a range from 2% to 99% of a total                concentration of the upstream NO_(x) compounds comprises                introducing at least one oxidizing agent into the flue                gas stream;                wherein the method regenerates the at least one filter                medium.    -   E94. The method of embodiment 93, wherein a temperature of the        flue gas stream ranges from 160° C. to 280° C. during the        flowing step.    -   E95. The method of embodiment 93 or embodiment 94, wherein the        flue gas stream further comprises Oxygen (O₂), Water (H₂O),        Nitrogen (N₂), Carbon Monoxide (CO), Sulfur Dioxide (SO₂),        Sulfur Trioxide (SO₃), one or more hydrocarbons, or any        combination thereof.    -   E96. The method of any of embodiments 93 to 95, wherein flowing        the flue gas stream transverse to the cross-section of the at        least one filter medium comprises flowing the flue gas stream        perpendicular to the cross-section of the at least one filter        medium.    -   E97. The method of any of embodiments 93 to 96, wherein the at        least one filter medium is disposed within at least one filter        bag, wherein the at least one filter bag is housed within at        least one filter bag housing, and wherein the at least one        catalyst material is in the form of catalyst particles.    -   E98. The method of embodiment 97, wherein the at least one        filter medium comprises:        -   a porous protective layer; and        -   a porous catalytic layer, wherein the porous catalytic layer            comprises the catalyst particles.    -   E99. The method of embodiment 98, wherein the porous protective        layer of the at least one filter medium comprises a microporous        layer, wherein the microporous layer comprises an expanded        polytetrafluoroethylene (ePTFE) membrane.    -   E100. The method of embodiment 98 or embodiment 99, wherein the        porous catalytic layer of the at least one filter medium        comprises at least one polymeric substrate.    -   E101. The method of any of embodiments 98 to 100, wherein the        porous catalytic layer comprises at least one ceramic substrate.    -   E102. The method of any of embodiments 98 to 101, wherein the        porous catalytic layer comprises polytetrafluorethylene (PTFE),        poly(ethylene-co-tetrafluoroethylene) (ETFE), ultra-high        molecular weight polyethylene (UHMWPE), polyparaxylylene (PPX),        polylactic acid, polyimide, polyamide, polyaramid, polyphenylene        sulfide, fiberglass, or any combination thereof.    -   E103. The method of any of embodiments 98 to 102, wherein the        catalyst particles are enmeshed within the porous catalytic        layer.    -   E104. The method of any of embodiments 98 to 103, wherein the        porous catalytic layer is in the form of a layered assembly        comprising:        -   a porous catalytic film; and        -   at least one felt batt, wherein the at least one felt batt            is positioned on at least one side of the porous catalytic            film.    -   E105. The method of embodiment 104, wherein the porous catalytic        film comprises an expanded polytetrafluoroethylene (ePTFE)        membrane.    -   E106. The method of embodiment 104, wherein the at least one        felt batt comprises: a polytetrafluoroethylene (PTFE) felt, a        PTFE fleece, an expanded polytetrafluoroethylene (ePTFE) felt,        an ePTFE fleece, a woven fluoropolymer staple fiber, a nonwoven        fluoropolymer staple fiber, or any combination thereof.    -   E107. The method of any of embodiments 93 to 106, wherein the at        least one catalyst material comprises at least one of: Vanadium        Monoxide (VO), Vanadium Trioxide (V₂O₃), Vanadium Dioxide (VO₂),        Vanadium Pentoxide (V₂O₅), Tungsten Trioxide (WO₃), Molybdenum        Trioxide (MoO₃), Titanium Dioxide (TiO₂), Silicon Dioxide        (SiO₂), Aluminum Trioxide (Al₂O₃), Manganese Oxide (MnO₂),        zeolites, or any combination thereof.    -   E108. The method of any of embodiments 93 to 107, wherein ABS        deposits are disposed on the catalyst material of the at least        one filter medium in a concentration ranging from 0.01% to 99%        by mass of the at least one filter medium during the providing        step.    -   E109. The method of any of embodiments 93 to 108, wherein, after        increasing the upstream NO₂ concentration to a range from 2% to        99% of a total concentration of the upstream NO_(x) compounds,        ABS deposits are disposed on the catalyst material of the at        least one filter medium in a concentration ranging from 0.01% to        98% by mass of the at least one filter medium.    -   E110. The method of any of embodiments 93 to 109, wherein the at        least one oxidizing agent is chosen from: hydrogen peroxide        (H₂O₂), ozone (O₃), hydroxyl radical, or any combination        thereof.    -   E111. The method of any of embodiments 93 to 110, wherein the        increasing of the NO_(x) removal efficiency further comprises        removing at least some of the ABS deposits, the AS deposits, or        any combination thereof, from the at least one filter medium.    -   E112. The method of embodiment 110 or 111, wherein the at least        one oxidizing agent is H₂O₂.    -   E113. The method of embodiment 112, wherein the H₂O₂ is        introduced into the flue gas stream in a sufficient amount so as        to oxidize at least some of the NO in the flue gas stream to        NO₂, wherein the oxidation of at least some of the NO in the        flue gas stream to NO₂ results in the NO₂ having the upstream        concentration of 2% to 99% of the total concentration of the        upstream NO_(x) compounds.    -   E114. The method of embodiment 113, wherein the oxidation of at        least some of the NO in the flue gas stream to NO₂ results in        the NO₂ having an upstream concentration of 25% to 50% of the        total concentration of the upstream NO_(x) compounds.    -   E115. The method of embodiment 113, wherein the sufficient        amount of H₂O₂ that is introduced into the flue gas stream is an        amount sufficient to oxidize at least 30% of the NO        concentration in the flue gas stream to NO₂.    -   E116. The method of embodiment 113, wherein the sufficient        amount of H₂O₂ that is introduced into the flue gas stream is an        amount sufficient to oxidize 30% to 50% of the NO concentration        in the flue gas stream to NO₂    -   E117. The method of embodiment 113, wherein the sufficient        amount of H₂O₂ that is introduced into the flue gas stream is        0.1 wt % H₂O₂ to 30 wt % H₂O₂ based on a total weight of the        flue gas stream.    -   E118. The method of any of embodiments 93 to 117, further        comprising adding ammonia (NH₃) to the flue gas stream.    -   E119. The method of embodiment 118, wherein the NH₃ is added a        concentration ranging from 0.0001% to 0.5% of the concentration        of the flue gas stream.    -   E120. A method comprising:        -   providing at least one filter medium            -   wherein the at least one filter medium comprises at                least one catalyst material;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium from an upstream side of the filter medium to            a downstream side of the filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);                -   Sulfur Dioxide (SO₂); and                -   Ammonia (NH₃);        -   maintaining a constant NO_(x) removal efficiency of the at            least one filter medium;            -   wherein the maintaining a constant NO_(x) removal                efficiency of the at least one filter medium comprises:                -   providing an NO₂ concentration, measured from the                    upstream side of the filter medium, in a range from                    2% to 99% of a total concentration of the NO_(x)                    compounds, wherein providing the NO₂ concentration,                    measured from the upstream side of the filter                    medium, in a range from 2% to 99% of a total                    concentration of the NO_(x) compounds comprises                    introducing at least one oxidizing agent into the                    flue gas stream; and                -   controlling the NO₂ concentration, measured from the                    downstream side of the filter medium, to a range of                    from 0.0001% to 0.5% of the concentration of the                    flue gas stream;                    wherein the method cleans the flue gas stream.    -   E121. A system comprising:        -   at least one filter medium,            -   wherein the at least one filter medium comprises:                -   an upstream side;                -   a downstream side;                -   at least one catalyst material; and                -   ammonium bisulfate (ABS) deposits, ammonium sulfate                    (AS) deposits, or any combination thereof;        -   at least one filter bag,            -   wherein the at least one filter medium is disposed                within the at least one filter bag; and        -   at least one filter bag housing,            -   wherein the at least one filter bag is disposed within                the at least one filter bag housing;            -   wherein the at least one filter bag housing is                configured to receive a flow of a flue gas stream                transverse to a cross-section of the at least one filter                medium, such that the flue gas stream passes through the                cross section of the at least one filter medium from the                upstream side of the at least one filter medium to the                downstream side of the at least one filter medium,                -   wherein the flue gas stream comprises:                -    NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂); and    -   wherein the system is configured to increase an NO_(x) removal        efficiency of the at least one filter medium when an upstream        NO₂ concentration is increased to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds, and        wherein the upstream NO₂ concentration is increased to a range        from 2% to 99% of a total concentration of the upstream NO_(x)        compounds by introducing at least one oxidizing agent into the        flue gas stream.    -   E122. A method comprising:        -   providing at least one filter medium            -   wherein the at least one filter medium comprises at                least one catalyst material;        -   flowing a flue gas stream transverse to a cross-section of            the at least one filter medium, such that the flue gas            stream passes through the cross section of the at least one            filter medium from an upstream side of the filter medium to            a downstream side of the filter medium;            -   wherein the flue gas stream comprises:                -   NO_(x) compounds comprising:                -    Nitric Oxide (NO), and                -    Nitrogen Dioxide (NO₂);                -   Sulfur Dioxide (SO₂); and                -   Ammonia (NH₃);        -   maintaining a NO_(x) removal efficiency of the at least one            filter medium in an amount of at least 70% of an initial            NO_(x) efficiency by:            -   providing an NO₂ concentration, measured from the                upstream side of the filter medium, in a range from 2%                to 99% of a total concentration of the NO_(x) compounds,                wherein providing the NO₂ concentration, measured from                the upstream side of the filter medium, in a range from                2% to 99% of a total concentration of the NO_(x)                compounds comprises introducing at least one oxidizing                agent into the flue gas stream; and            -   controlling NO₂ concentration, measured from the                downstream side of the filter medium, to a range of from                0.0001% to 0.5% of the concentration of the flue gas                stream;                wherein the method cleans the flue gas stream.    -   E123. A filter medium comprising:        -   an upstream side;        -   a downstream side;        -   at least one catalyst material; and        -   ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)            deposits, or any combination thereof;    -   wherein the filter medium is configured to receive a flow of a        flue gas stream transverse to a cross-section of the filter        medium, such that the flue gas stream passes through the cross        section of the at least one filter medium from the upstream side        of the filter medium to the downstream side of the filter        medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂); and    -   wherein the at least one filter medium is configured to increase        a NO_(x) removal efficiency of the at least one filter medium        upon an increase of upstream NO₂ to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds, wherein        the increase of upstream NO₂ to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds comprises        introducing at least one oxidizing agent into the flue gas        stream.    -   E124. A filter medium comprising:        -   an upstream side;        -   a downstream side;        -   at least one catalyst material; and        -   ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)            deposits, or any combination thereof;    -   wherein the filter medium is configured to receive a flow of a        flue gas stream transverse to a cross-section of the filter        medium, such that the flue gas stream passes through the cross        section of the at least one filter medium from the upstream side        of the filter medium to the downstream side of the filter        medium;        -   wherein the flue gas stream comprises:            -   NO_(x) compounds comprising:                -   Nitric Oxide (NO), and                -   Nitrogen Dioxide (NO₂); and    -   wherein the at least one filter medium is configured to increase        a NO_(x) removal efficiency of the at least one filter medium        upon an increase of upstream NO₂ to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds, wherein        the increase of upstream NO₂ to a range from 2% to 99% of a        total concentration of the upstream NO_(x) compounds comprises        introducing additional NO₂ into the flue gas stream.

EXAMPLES Example 1: In-Situ “Flow-Through” Regeneration of Filter MediumIncluding a Catalyst Coated Composite Article by NO and NO₂ Gas Mixture

An exemplary filter medium including a non-limiting example of acatalyst material in the form of a catalyst coated composite article wasprepared on a porous substrate having active catalyst particles adheredto the surface by a polymer adhesive according to U.S. Pat. No.6,331,351.

In-Situ “Flow-Through” Regeneration by NO and NO₂ Mixture

The filter medium including the catalyst coated composite sample wasreturned from the field after exposure to a flue gas stream. Thedeposition of ammonium bisulfate on the returned sample was confirmed byFourier-transform infrared spectroscopy (FTIR, Thermal Nicolet iS50).During an in-situ regeneration, a 4.5 inch (˜1.77 cm)×4.5 inch (˜1.77cm) sample filter medium including a catalyst coated composite samplewas placed in a reactor. A gas mixture including 310 ppm NO, 330 ppmNO₂, 4% O₂, 8% water moisture and N₂ was set to flow-through thecatalyst coated composite sample at 230° C. with a total flowrate of 2L/min. The gas phase NO and NO₂ concentration were monitored with a MKSMULTI-GAS' 2030D FTIR analyzer (MKS Instruments, Andover, Mass.). The NOand NO₂ gas mixture was obtained by partially oxidizing NO to NO₂ by O₃generated from the TG-20 O₃ generator (Ozone solutions, Hull, Iowa).NO_(x) removal efficiency was measured before in-situ regenerationtreatment and 2, 4, 6, 8, 10 hours after in-situ regeneration treatment.

NO_(x) Reaction Efficiency

The filter medium including the catalyst coated composite article wastested for catalytic NO_(x) removal efficiency from a simulated flue gasat 230° C. The simulated flue gas contained 200 ppm NO, 200 ppm NH₃, 5%O₂, and N₂ with a total flowrate of 3.4 L/min. To determine NO_(x)removal efficiency, the upstream (i.e., the concentration of NO_(x)entering into the chamber before exposure to the filter medium) anddownstream concentration (i.e. the concentration of NO_(x) exiting thechamber after exposure to the filter medium) of NO were monitored with aMKS MULTI-GAS™ 2030D FTIR analyzer (MKS Instruments, Andover, Mass.).NO_(x) removal efficiency was calculated according to the followingformula where ‘NO’ indicates the concentration of NO in the respectivestream.

NO_(x) removal efficiency (“DeNO_(x)”) (%)=(NO in−NO out)/NO in×100%.

Results are shown in FIG. 2. The improved NO_(x) removal efficiency overtime, shown in FIG. 2, demonstrates that the filter medium wassuccessfully regenerated.

Example 2: In-Situ “Flow-Through” Regeneration of Filter MediumIncluding a Catalytic Composite Article by NO and NO₂ Gas Mixture

A filter medium including a catalytic composite article is formedaccording to International Publication No. WO 2019/099025. The filtermedium included a catalytic composite article having a layered assemblythat included a polytetrafluoroethylene (PTFE)+catalyst compositemembrane having a first, upstream side and a second, downstream side;and one or more felt batts. Each felt batt was formed of fleece formedfrom PTFE staple fiber. The filter medium was connected together by aplurality of perforations formed by a needle punching process, by aneedling process, or both.

The PTFE+catalyst composite membrane of the filter medium describedabove were prepared using the general dry blending methodology taught inU.S. Pat. No. 7,791,861. to form composite tapes that were thenuniaxially expanded according to the teachings of U.S. Pat. No.3,953,556. The resulting porous fibrillated expanded PTFE (ePTFE)composite membranes included supported catalyst particles durablyenmeshed and immobilized with the ePTFE node and fibril matrix.

In-Situ “Flow-Through” Regeneration by NO and NO₂ Mixture

The sample filter medium including the sample catalytic compositearticle described above was in-situ fouled by 400 ppm NO, 440 ppm NH₃,3000 ppm SO₂ and 8% water moisture at 230° C. and returned fromInnovative combustion Technologies (ICT). During an in-situregeneration, a particular filter medium including a square catalyticcomposite sample (4.5 inch×4.5 inch) returned from ICT was placed in areactor. A gas mixture including 330 ppm NO, 330 ppm NO₂, 4% O₂, 8%water moisture, and N₂ was set to flow-through the catalytic compositesample at 230° C. with a total flowrate of 2 L/min. The NO and NO₂ gasmixture was obtained by partially oxidizing NO to NO₂ by O₃ generatedfrom the TG-20 O₃ generator (Ozone solutions, Hull, Iowa). NO_(x)removal efficiency was measured before in-situ regeneration treatmentand 4, 10, 15, 21, 24 hours after in-situ regeneration treatment. Thedownstream (i.e. the concentration of NO_(x) exiting the chamber afterexposure to the filter medium) gas phase NO and NO₂ concentrations weremonitored with a MKS MULTI-GAS™ 2030D FTIR analyzer (MKS Instruments,Andover, Mass.).

NO_(x) Reaction Efficiency

The filter medium including the sample catalytic composite article wastested for catalytic NO_(x) removal efficiency at 230° C. from asimulated flue gas. The simulated flue gas contained 200 ppm NO, 200 ppmNH₃, 5 vol % O₂, 5% water moisture, and N₂ with a total flowrate of 3.4L/min. In order to determine NO_(x) removal efficiency, the upstream(i.e., the concentration of NO_(x) entering into the chamber beforeexposure to the filter medium) and downstream concentration (i.e. theconcentration of NO_(x) exiting the chamber relative after exposure tothe filter medium) of NO were monitored with a MKS MULTI-GAS™ 2030D FTIRanalyzer (MKS Instruments, Andover, Mass.). NO_(x) removal efficiencywas calculated according to the following formula where ‘NO’ indicatesthe concentration of NO in the respective stream.

NO_(x) removal efficiency (“DeNO_(x)”) (%)=(NO in−NO out)/NO in×100%

Relative DeNO_(x) removal efficiency (%)=DeNO_(x) afterregeneration/DeNO_(x) of a fresh control sample.

Results are shown in FIGS. 3 and 4. The improved NO_(x) removalefficiency over time, shown in FIGS. 3 and 4, demonstrates that thefilter medium was successfully regenerated.

Example 3: In-Situ “Flow-Through” Regeneration of Filter MediumIncluding a Catalytic Composite Article by NO, NO₂ and NH₃ Gas Mixture

A catalytic composite article was used as described in Example 2.

In-Situ Flow-Through Regeneration by NO, NO₂, and NH₃ Mixture

Sample filter medium including the sample catalytic composite articledescribed in Example 2 in-situ fouled by 400 ppm NO, 440 ppm NH₃, 3000ppm SO₂ and 8% water moisture at 230° C. and returned from Innovativecombustion Technologies (ICT). During an in-situ regeneration, aparticular filter medium including a square catalytic composite sample(4.5 inch×4.5 inch) returned from ICT was placed in a reactor. A gasmixture including 330 ppm NO, 330 ppm NO₂, 85 ppm NH₃, 4% O₂, 8% watermoisture, and N₂ was set to flow-through the catalytic composite sampleat 230° C. with a total flowrate of 2 L/min. The NO+NO₂ gas mixture wasobtained by partially oxidizing NO to NO₂ by O₃ generated from the TG-20O₃ generator (Ozone solutions, Hull, Iowa). NO_(x) removal efficiencywas measured before in-situ regeneration treatment and 4, 10, 15, 21hours after in-situ regeneration treatment. The downstream (i.e. theconcentration of NO_(x) exiting the chamber after exposure to the filtermedium) gas phase NO and NO₂ concentrations were monitored with a MKSMULTI-GAS™ 2030D FTIR analyzer (MKS Instruments, Andover, Mass.).

NO_(x) Reaction Efficiency

The filter medium including the sample catalytic composite article wastested for catalytic NO_(x) removal efficiency at 230° C. from asimulated flue gas as described in Example 2.

NO_(x) removal efficiency (“DeNO_(x)”) (%)=(NO in−NO out)/NO in×100%

Relative DeNO_(x) removal efficiency (%)=DeNO_(x) afterregeneration/DeNO_(x) of a fresh control sample.

Results are shown in FIGS. 5 and 6. The improved NO_(x) removalefficiency over time, shown in FIGS. 5 and 6, demonstrates that thefilter medium was successfully regenerated.

Example 4: In-Situ “Flow-By” Regeneration of Filter Medium Including aCatalytic Composite Article by NO, NO₂ and NH₃ Gas Mixture

A catalytic composite article as described in Example 2 was used.

In-Situ “Flow-By” Regeneration by NO, NO₂, and NH₃ Mixture

A sample filter medium including the sample catalytic composite articledescribed in Example 2 in-situ fouled by 400 ppm NO, 440 ppm NH₃, 3000ppm SO₂ and 8% water moisture at 230° C. and returned from Innovativecombustion Technologies (ICT). During an in-situ regeneration, aparticular filter medium including a square catalytic composite sample(4.5 inch×4.5 inch) returned from ICT was wrapped around a hollowelliptic cylinder stainless steel mesh and placed in a reactor. A gasmixture including 330 ppm NO, 330 ppm NO₂, 85 ppm NH₃, 4% O₂, 8% watermoisture, and N₂ was set to flow-by the catalytic composite sample at230° C. with a total flowrate of 2 L/min. The NO+NO₂ gas mixture wasobtained by partially oxidizing NO to NO₂ by O₃ generated from the TG-20O₃ generator (Ozone solutions, Hull, Iowa). NO_(x) removal efficiencywas measured before in-situ regeneration treatment and 4 hours afterin-situ regeneration treatment.

NO_(x) Reaction Efficiency

The filter medium including the sample catalytic composite article wastested for catalytic NO_(x) removal efficiency at 230° C. from asimulated flue gas as described in Example 2.

NO_(x) removal efficiency (“DeNO_(x)”) (%)=(NO in−NO out)/NO in×100%

Relative DeNO_(x) removal efficiency (%)=DeNO_(x) afterregeneration/DeNO_(x) of a fresh control sample.

Results are shown in FIG. 7. The improved NO_(x) removal efficiency overtime, shown in FIG. 7, demonstrates that the filter medium wassuccessfully regenerated.

Example 5: In-Situ “Flow-Through” Regeneration of Filter MediumIncluding Catalytic Filter Bags by NO, NO₂ and NH₃ Gas Mixture

Four catalytic filter bags (65 mm in diameter, 1630 mm in length) wereprepared from the catalytic composite articles described in Example 2.

In-Situ Deposition of Ammonium Bisulfate

The filter medium including the sample catalytic filter bags werein-situ fouled at Innovative combustion Technologies by 200 ppm NO, 240ppm NH₃, 3000 ppm SO₂ and 8% water moisture at 230° C. for 4 hours.

In-Situ “Flow-Through” Regeneration by NO, NO_(x), and NH₃ Mixture

During an in-situ regeneration, a particular filter medium including 4catalytic filter bags in-situ fouled as described above were used. A gasmixture including 30 ppm NO, 30 ppm NO₂, 8 ppm NH₃, 10% O₂, 8% watermoisture, and N₂ was set to flow-through the catalytic filter bags at230° C. with a total flowrate of 25.3 SCFM for 20 hours.

NO_(x) Reaction Efficiency

The filter medium including the sample catalytic filter bags were testedfor NO_(x) removal efficiency at Innovative Combustion Technologies froma simulated flue gas at 230° C. The simulated flue gas contained 200 ppmNO, 190 ppm NH₃, 10% O₂, 8% water moisture, and N₂ with a total flowrateof 25.3 standard cubic feet per minute (SCFM). In order to determineNO_(x) removal efficiency, the upstream (i.e., the concentration ofNO_(x) entering into the chamber before exposure to the filter medium)and downstream concentration (i.e. the concentration of NO_(x) exitingthe chamber relative after exposure to the filter medium) of NO and NO₂were monitored with a MKS MULTI-GAS™ 2030D FTIR analyzer (MKSInstruments, Andover, Mass.). NO_(x) removal efficiency was calculatedaccording to the following formula where ‘NO_(x)’ indicates the totalconcentration of NO and NO₂ in the respective stream.

NO_(x) removal efficiency (“DeNO_(x) efficiency”) (%)=(NO_(x) in−NO_(x)out)/NO_(x) in×100%.

Results are shown in FIG. 8. The improved NO_(x) removal efficiency overtime, shown in FIG. 8, demonstrates that the filter medium wassuccessfully regenerated.

Example 6: Long Term NO_(x) Removal Reaction with Exposure to SO₂

A catalytic composite article as described in Example 2 was used.

Long Term Flow-Through DeNO_(x) Reaction by NO, NO₂, and NH₃ Mixture(with and without Excess NO₂ in the Downstream Side of the FilterMedium)

The filter medium including the sample catalytic composite article wastested for catalytic NO_(x) removal efficiency from a simulated flue gasat 230° C. The simulated flue gas included 13.5 ppm SO₂, 200 ppm NO_(x)(NO+NO₂), 200 ppm NH₃, 5% O₂, 5% water moisture, and N₂ with a totalflowrate of 3.4 L/min. The NO₂ was introduced from a gas cylinder. Theinlet NO₂ concentration was controlled to have excess NO₂ (1-8 pm) andno excess NO₂ in the downstream (i.e. the concentration of NO_(x)exiting the chamber after exposure to the filter medium). In order todetermine NO_(x) removal efficiency, the upstream (i.e., theconcentration of NO_(x) entering into the chamber before exposure to thefilter medium) and downstream concentration of NO and NO₂ were monitoredwith a MKS MULTI-GAS™ 2030D FTIR analyzer (MKS Instruments, Andover,Mass.). NO_(x) removal efficiency was calculated according to thefollowing formula where ‘NO_(x)’ indicates the total concentration of NOand NO₂ in the respective stream.

NO_(x) removal efficiency (“DeNO_(x) efficiency”) (%)=(NO_(x) in−NO_(x)out)/NO_(x) in×100%.

Results are shown in FIGS. 9-11.

Example 7: In-Situ “Flow-Through” Regeneration of Filter MediumIncluding a Catalytic Composite Article by NO, NO₂ and NH₃ Gas Mixturewith Exposure to SO₂

A catalytic composite article was used as described in Example 2.

In-Situ Flow-Through Regeneration by NO, NO_(x), and NH₃ Mixture withExposure to SO₂ (with Controlled NO₂ Slip in the Downstream Side of theFilter Medium)

Sample filter medium including the sample catalytic composite articledescribed in Example 2 was in-situ fouled by 400 ppm NO, 440 ppm NH₃,3000 ppm SO₂ and 8% water moisture at 230° C. and returned fromInnovative combustion Technologies (ICT). During an in-situregeneration, a particular filter medium including a square catalyticcomposite sample (4.5 inch×4.5 inch) returned from ICT was placed in areactor. Catalytic NO_(x) removal efficiency before regeneration (in theperiod of 0-2 hours), during regeneration (in the period of 3-51 hours)and after regeneration (in the period of 55-60 hours) were shown in FIG.12. Catalytic NO_(x) removal efficiency before and after regenerationwere tested at 230° C. with 200 ppm NO, 200 ppm NH₃, 5% O₂, 5% watermoisture, and N₂ with a total flowrate of 3.4 L/min. During theregeneration, the simulated flue gas included 13.5 ppm SO₂, 200 ppmNO_(x) (NO+NO₂), 200 ppm NH₃, 5% O₂, 5% water moisture, and N₂ with atotal flowrate of 3.4 L/min. The inlet NO₂ concentration was controlledto have excess NO₂ (1-5 ppm, FIG. 12) slip in the downstream (i.e. theconcentration of NO_(x) exiting the chamber after exposure to the filtermedium). The NO₂ was introduced from a gas cylinder.

In order to determine NO_(x) removal efficiency, the upstream (i.e., theconcentration of NO_(x) entering into the chamber before exposure to thefilter medium) and downstream concentration of NO and NO₂ were monitoredwith a MKS MULTI-GAS™ 2030D FTIR analyzer (MKS Instruments, Andover,Mass.). NO_(x) removal efficiency was calculated according to thefollowing formula where ‘NO_(x)’ indicates the total concentration of NOand NO₂ in the respective stream.

NO_(x) removal efficiency (“DeNO_(x) efficiency”) (%)=(NO_(x) in−NO_(x)out)/NO_(x) in×100%.

Results are shown in FIG. 12.

Example 8: In-Situ “Flow-Through” Regeneration of Filter MediumIncluding a Catalytic Composite Article by NO, NO₂ and NH₃ Gas Mixturewith Exposure to SO₂

A catalytic composite article was used as described in Example 2.

In-Situ Flow-Through Regeneration by NO, NO_(x), and NH₃ Mixture withExposure to SO₂ (with Controlled NO₂ Slip in the Downstream Side of theFilter Medium)

Sample filter medium including the sample catalytic composite articledescribed in Example 2 was in-situ fouled by 400 ppm NO, 440 ppm NH₃,3000 ppm SO₂ and 8% water moisture at 230° C. and returned fromInnovative combustion Technologies (ICT). During an in-situregeneration, a particular filter medium including a square catalyticcomposite sample (4.5 inch×4.5 inch) returned from ICT was placed in areactor. Before the in-situ regeneration, catalytic NO_(x) removalefficiency (FIG. 13) was tested at 230° C. with 200 ppm NO, 200 ppm NH₃,5% O₂, 5% water moisture, and N₂ with a total flowrate of 3.4 L/min.After checking the NO_(x) removal efficiency before regeneration, a 6.2days (148 hours) in-situ flow-through regeneration was conducted. Duringthe regeneration, the simulated flue gas included 13.5 ppm SO₂, 200 ppmNO_(x) (NO+NO₂), 200 ppm NH₃, 5% O₂, 5% water moisture, and N₂ with atotal flowrate of 3.4 L/min. The inlet NO₂ concentration was controlledto have excess NO₂ (1-12 ppm) slip in the downstream (i.e. theconcentration of NO_(x) exiting the chamber after exposure to the filtermedium). The NO₂ was introduced from a gas cylinder. Catalytic NO_(x)removal efficiency during the in-situ regeneration was shown in FIG. 13.After the in-situ regeneration, catalytic NO_(x) removal efficiency wastested at 230° C. with 200 ppm NO, 200 ppm NH₃, 5% O₂, 5% watermoisture, and N₂ with a total flowrate of 3.4 L/min, shown in FIG. 13.

To determine NO_(x) removal efficiency, the upstream (i.e., theconcentration of NO_(x) entering into the chamber before exposure to thefilter medium) and downstream concentration of NO and NO₂ were monitoredwith a MKS MULTI-GAS™ 2030D FTIR analyzer (MKS Instruments, Andover,Mass.). NO_(x) removal efficiency was calculated according to thefollowing formula where ‘NO_(x)’ indicates the total concentration of NOand NO₂ in the respective stream.

NO_(x) removal efficiency (“DeNO_(x) efficiency”) (%)=(NO_(x) in−NO_(x)out)/NO_(x) in×100%.

Results are shown in FIG. 13.

Example 9: Long Term NO_(x) Removal Reaction with Exposure to SO₂ withPeriodic In-Situ “Flow-Through” Regeneration of Filter Medium

A catalytic composite article was used as described in Example 2.

Periodic In-Situ Flow-Through Regeneration by NO, NO_(x), and NH₃Mixture with Exposure to SO₂ (with Controlled NO₂ Slip in the DownstreamSide of the Filter Medium)

The filter medium including the sample catalytic composite articledescribed in Example 2 was tested for catalytic NO_(x) removalefficiency from a simulated flue gas at 230° C. for over 400 hours (16.7days). The simulated flue gas included 13.5 ppm SO₂, 200 ppm NO, 200 ppmNH₃, 5% O₂, 5% water moisture, and N₂ with a total flowrate of 3.4L/min. The DeNO_(x) removal efficiency change with time was shown inFIG. 10 and used as raw data (Tested DeNO_(x) in FIG. 14) to extrapolatethe long term DeNO_(x) removal efficiency (Simulated DeNO_(x) in FIG.14) change with operation time. In-situ flow-through regeneration by NO,NO₂, and NH₃ mixture (with controlled NO₂ slip in the downstream side ofthe filter medium) will be started once the DeNO_(x) removal efficiencydecreased to 72%, or 78% of the initial DeNO_(x) removal efficiency(initial DeNO_(x) removal efficiency was 92%, FIG. 14). According toExample 8, after 148 hours (6.2 days) in-situ flow-through regenerationby NO, NO₂, and NH₃ mixture (with controlled NO₂ slip in the downstreamside of the filter medium), the DeNO_(x) removal efficiency can berecovered to 83%, or 90% of the initial DeNO_(x) removal efficiency(FIG. 14). After the first regeneration, periodic in-situ flow-throughregeneration can be conducted periodically once the DeNO_(x) removalefficiency decreased to 72% or 78% of the initial DeNO_(x) removalefficiency. This process is illustrated in FIG. 14.

Example 10: Injection of 1 wt % H₂O₂ Solution into a Simulated Flue GasStream Comprising SO₂ and NO

A syringe pump was used to inject 6.1 ml of 1 wt % H₂O₂ solution at aspeed of 12.0 ml/hour into a simulated flue gas stream having a flowrate of 3.19 L/min. The simulated flue gas stream comprised 35 ppm SO₂and 200 ppm NO. The concentration of NO and NO₂ before, during and afterthe H₂O₂ injection was measured at several different temperatures,namely 174° C., 189° C., 195° C., and 204° C., by a MKS MULTI-GAS™ 2030DFTIR analyzer (MKS Instruments, Andover, Mass.).

NO to NO₂ conversion efficiency was calculated based on the NO and NO₂concentration during the H₂O₂ injection, NO to NO₂ conversion efficiency(“NO to NO₂ conversion”) (%)=NO₂/(NO+NO₂)×100%.

Results are shown in FIGS. 15 and 16. As shown in FIGS. 15 and 16,NO_(x) removal efficiency can be improved by introducing at least oneoxidizing agent, such as but not limited to H₂O₂, into a flue gasstream.

Example 11: Injection of 0.3 wt % H₂O₂ Solution into a Simulated FlueGas Stream Comprising SO₂ and NO

A syringe pump was used to inject 6.1 ml of 0.3 wt % H₂O₂ solution at aspeed of 12.0 ml/hour into a simulated flue gas stream. The simulatedflue gas stream had a flow rate of 3.19 L/min and comprised 35 ppm SO₂and 200 ppm NO. The concentration of NO and NO₂ before, during and afterthe H₂O₂ injection was measured at two different temperatures, namely152° C. and 190° C., by a MKS MULTI-GAS™ 2030D FTIR analyzer (MKSInstruments, Andover, Mass.).

NO to NO₂ conversion efficiency was calculated based on the NO and NO₂concentration during the H₂O₂ injection, NO to NO₂ conversion efficiency(“NO to NO₂ conversion”) (%)=NO₂/(NO+NO₂)×100%.

Results are shown in FIG. 17. As shown in FIG. 17, NO_(x) removalefficiency can be improved by introducing at least one oxidizing agent,such as but not limited to H₂O₂, into a flue gas stream.

Variations, modifications and alterations to embodiments of the presentdisclosure described above will make themselves apparent to thoseskilled in the art. All such variations, modifications, alterations andthe like are intended to fall within the spirit and scope of the presentdisclosure, limited solely by the appended claims.

While several embodiments of the present disclosure have been described,it is understood that these embodiments are illustrative only, and notrestrictive, and that many modifications may become apparent to those ofordinary skill in the art. For example, all dimensions discussed hereinare provided as examples only, and are intended to be illustrative andnot restrictive.

Any feature or element that is positively identified in this descriptionmay also be specifically excluded as a feature or element of anembodiment of the present as defined in the claims.

The disclosure described herein may be practiced in the absence of anyelement or elements, limitation or limitations, which is notspecifically disclosed herein. Thus, for example, in each instanceherein, any of the terms “comprising,” “consisting essentially of and“consisting of” may be replaced with either of the other two terms. Theterms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within.

1. A method comprising: providing at least one filter medium; whereinthe at least one filter medium comprises: at least one catalystmaterial; and ammonium bisulfate (ABS) deposits, ammonium sulfate (AS)deposits, or any combination thereof; flowing a flue gas streamtransverse to a cross-section of the at least one filter medium, suchthat the flue gas stream passes through the cross section of the atleast one filter medium, wherein the flue gas stream comprises: NO_(x)compounds comprising: Nitric Oxide (NO), and Nitrogen Dioxide (NO₂); andincreasing NO_(x) removal efficiency of the at least one filter medium;wherein the increasing of the NO_(x) removal efficiency of the at leastone filter medium comprises increasing an upstream NO₂ concentration toa range from 2% to 99% of a total concentration of the upstream NO_(x)compounds, wherein increasing the upstream NO₂ concentration to a rangefrom 2% to 99% of a total concentration of the upstream NO_(x) compoundscomprises introducing at least one oxidizing agent into the flue gasstream.
 2. The method of claim 1, wherein a temperature of the flue gasstream ranges from 160° C. to 280° C. during the flowing step.
 3. Themethod of claim 1, wherein the flue gas stream further comprises Oxygen(O₂), Water (H₂O), Nitrogen (N₂), Carbon Monoxide (CO), Sulfur Dioxide(SO₂), Sulfur Trioxide (SO₃), one or more hydrocarbons, or anycombination thereof.
 4. The method of claim 1, wherein flowing the fluegas stream transverse to the cross-section of the at least one filtermedium comprises flowing the flue gas stream perpendicular to thecross-section of the at least one filter medium.
 5. The method of claim1, wherein the at least one filter medium is disposed within at leastone filter bag, wherein the at least one filter bag is housed within atleast one filter bag housing, and wherein the at least one catalystmaterial is in the form of catalyst particles.
 6. The method of claim 5,wherein the at least one filter medium comprises: a porous protectivelayer; and a porous catalytic layer, wherein the porous catalytic layercomprises the catalyst particles.
 7. The method of claim 6, wherein theporous protective layer of the at least one filter medium comprises amicroporous layer, wherein the microporous layer comprises an expandedpolytetrafluoroethylene (ePTFE) membrane.
 8. The method of claim 6,wherein the porous catalytic layer of the at least one filter mediumcomprises at least one polymeric substrate.
 9. The method of claim 6,wherein the porous catalytic layer comprises at least one ceramicsubstrate.
 10. The method of claim 6, wherein the porous catalytic layercomprises polytetrafluorethylene (PTFE),poly(ethylene-co-tetrafluoroethylene) (ETFE), ultra-high molecularweight polyethylene (UHMWPE), polyparaxylylene (PPX), polylactic acid,polyimide, polyamide, polyaramid, polyphenylene sulfide, fiberglass, orany combination thereof.
 11. The method of claim 6 wherein the catalystparticles are enmeshed within the porous catalytic layer.
 12. The methodof claim 6, wherein the porous catalytic layer is in the form of alayered assembly comprising: a porous catalytic film; and at least onefelt batt, wherein the at least one felt batt is positioned on at leastone side of the porous catalytic film.
 13. The method of claim 12,wherein the porous catalytic film comprises an expandedpolytetrafluoroethylene (ePTFE) membrane.
 14. The method of claim 12,wherein the at least one felt batt comprises: a polytetrafluoroethylene(PTFE) felt, a PTFE fleece, an expanded polytetrafluoroethylene (ePTFE)felt, an ePTFE fleece, a woven fluoropolymer staple fiber, a nonwovenfluoropolymer staple fiber, or any combination thereof.
 15. The methodof claim 1, wherein the at least one catalyst material comprises atleast one of: Vanadium Monoxide (VO), Vanadium Trioxide (V₂O₃), VanadiumDioxide (VO₂), Vanadium Pentoxide (V₂O₅), Tungsten Trioxide (WO₃),Molybdenum Trioxide (MoO₃), Titanium Dioxide (TiO₂), Silicon Dioxide(SiO₂), Aluminum Trioxide (Al₂O₃), Manganese Oxide (MnO₂), zeolites, orany combination thereof.
 16. The method of claim 1, wherein ABS depositsare disposed on the catalyst material of the at least one filter mediumin a concentration ranging from 0.01% to 99% by mass of the at least onefilter medium during the providing step.
 17. The method of claim 1,wherein, after increasing the upstream NO₂ concentration to a range from2% to 99% of a total concentration of the upstream NO_(x) compounds, ABSdeposits are disposed on the catalyst material of the at least onefilter medium in a concentration ranging from 0.01% to 98% by mass ofthe at least one filter medium.
 18. The method of claim 1, wherein theat least one oxidizing agent is chosen from: hydrogen peroxide (H₂O₂),ozone (O₃), hydroxyl radical, or any combination thereof.
 19. The methodof claim 1, wherein the increasing of the NO_(x) removal efficiencyfurther comprises removing at least some of the ABS deposits, the ASdeposits, or any combination thereof, from the at least one filtermedium.
 20. The method of claim 18, wherein the at least one oxidizingagent is H₂O₂.
 21. The method of claim 20, wherein the H₂O₂ isintroduced into the flue gas stream in a sufficient amount so as tooxidize at least some of the NO in the flue gas stream to NO₂, whereinthe oxidation of at least some of the NO in the flue gas stream to NO₂results in the NO₂ having the upstream concentration of 2% to 99% of thetotal concentration of the upstream NO_(x) compounds.
 22. The method ofclaim 21, wherein the oxidation of at least some of the NO in the fluegas stream to NO₂ results in the NO₂ having an upstream concentration of25% to 50% of the total concentration of the upstream NO_(x) compounds.23. The method of claim 21, wherein the sufficient amount of H₂O₂ thatis introduced into the flue gas stream is an amount sufficient tooxidize at least 30% of the NO concentration in the flue gas stream toNO₂.
 24. The method of claim 21, wherein the sufficient amount of H₂O₂that is introduced into the flue gas stream is an amount sufficient tooxidize 30% to 50% of the NO concentration in the flue gas stream toNO₂.
 25. The method of claim 21, wherein the sufficient amount of H₂O₂that is introduced into the flue gas stream is 0.1 wt % H₂O₂ to 30 wt %H₂O₂ based on a total weight of the flue gas stream.
 26. The method ofclaim 1, further comprising adding ammonia (NH₃) to the flue gas stream.27. The method of claim 24, wherein the NH₃ is added a concentrationranging from 0.0001% to 0.5% of the concentration of the flue gasstream.
 28. A method comprising: providing at least one filter mediumwherein the at least one filter medium comprises at least one catalystmaterial; flowing a flue gas stream transverse to a cross-section of theat least one filter medium, such that the flue gas stream passes throughthe cross section of the at least one filter medium from an upstreamside of the filter medium to a downstream side of the filter medium;wherein the flue gas stream comprises: NO_(x) compounds comprising:Nitric Oxide (NO), and Nitrogen Dioxide (NO₂); Sulfur Dioxide (SO₂); andAmmonia (NH₃); maintaining a constant NO_(x) removal efficiency of theat least one filter medium; wherein the maintaining a constant NO_(x)removal efficiency of the at least one filter medium comprises:providing an NO₂ concentration, measured from the upstream side of thefilter medium, in a range from 2% to 99% of a total concentration of theNO_(x) compounds, wherein providing the NO₂ concentration, measured fromthe upstream side of the filter medium, in a range from 2% to 99% of atotal concentration of the NO_(x) compounds comprises introducing atleast one oxidizing agent into the flue gas stream; and controlling theNO₂ concentration, measured from the downstream side of the filtermedium, to a range of from 0.0001% to 0.5% of the concentration of theflue gas stream.
 29. A system comprising: at least one filter medium,wherein the at least one filter medium comprises: an upstream side; adownstream side; at least one catalyst material; and ammonium bisulfate(ABS) deposits, ammonium sulfate (AS) deposits, or any combinationthereof; at least one filter bag, wherein the at least one filter mediumis disposed within the at least one filter bag; and at least one filterbag housing, wherein the at least one filter bag is disposed within theat least one filter bag housing; wherein the at least one filter baghousing is configured to receive a flow of a flue gas stream transverseto a cross-section of the at least one filter medium, such that the fluegas stream passes through the cross section of the at least one filtermedium from the upstream side of the at least one filter medium to thedownstream side of the at least one filter medium, wherein the flue gasstream comprises: NO_(x) compounds comprising: Nitric Oxide (NO), andNitrogen Dioxide (NO₂); and wherein the system is configured to increasean NO_(x) removal efficiency of the at least one filter medium when anupstream NO₂ concentration is increased to a range from 2% to 99% of atotal concentration of the upstream NO_(x) compounds, and wherein theupstream NO₂ concentration is increased to a range from 2% to 99% of atotal concentration of the upstream NO_(x) compounds by introducing atleast one oxidizing agent into the flue gas stream.
 30. A methodcomprising: providing at least one filter medium wherein the at leastone filter medium comprises at least one catalyst material; flowing aflue gas stream transverse to a cross-section of the at least one filtermedium, such that the flue gas stream passes through the cross sectionof the at least one filter medium from an upstream side of the filtermedium to a downstream side of the filter medium; wherein the flue gasstream comprises: NO_(x) compounds comprising: Nitric Oxide (NO), andNitrogen Dioxide (NO₂); Sulfur Dioxide (SO₂); and Ammonia (NH₃);maintaining a NO_(x) removal efficiency of the at least one filtermedium in an amount of at least 70% of an initial NO_(x) efficiency by:providing an NO₂ concentration, measured from the upstream side of thefilter medium, in a range from 2% to 99% of a total concentration of theNO_(x) compounds, wherein providing the NO₂ concentration, measured fromthe upstream side of the filter medium, in a range from 2% to 99% of atotal concentration of the NO_(x) compounds comprises introducing atleast one oxidizing agent into the flue gas stream; and controlling NO₂concentration, measured from the downstream side of the filter medium,to a range of from 0.0001% to 0.5% of the concentration of the flue gasstream.